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EK/,T.;'.V"!.;. :; [i.'.nR!! 



INLAND NAVIGATION. 



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fiWlMWELL & HARftIS 



PRINCIPLES AND PRACTICE 



CANAL AND RIVER 

ENGHSrEERING 



BY 

DAVID STEVENSON, F.R.S.E. 

KEMBKB OfTbi DiniTllTIOlI OF dfii. KHauuiii ; 
3H OF "a BEMICH OF TH* CITIT, XSOnrXKBIHa OF ITOBIB AHZKICA," 



SECOND EDITION. 



EDINBURGH 
ADAM AND CHARLES BLACK 

1872. 



[Tht right iff TnauJaUen rtttned.] 

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PIUVTCD 8T T. AHD A. 



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PREFACE TO SECOND EDITION. 

SoHE of the information contained in the following 
Chapters was published as the article " Inland Naviga- 
tion," in the eightit edition of the Encyclopeedia Bri- 
tanmca, and was afi^rwards, in 1858, issued by the 
publishers as a eeparate work, which has for some time 
been out of print. 

Meears. Black hare asked me to prepare another 
edition ; and in complying with their request it has been 
thought right, not only to notice everything that could 
be regarded as new in Canal and River Engineering, but 
also to alter and ezt^id the original matter, instead of 
retaining the condensed style of the £rst issue, which was 
more suitable for the coltmma of an encydopeedia than 
the pages of an independent treatise. 

The reader will find in the first two chapters a sketch 
of the early history of Barge Canals, and a statemoit 
of the chief features of their construction, followed by a 
notice of those larger works used by sea-borne vessels, 
whicQi are divided into three distinct classes, represented 
hy the Caledonian, the Amsterdam, and the Suez Canals, 
of which I have given a description. 

345554 

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The Becoud part of the subject, relating to Rivers and 
Estuaries, embraces a much wider field of inquiry, and 
includes some of the most difiiciilt problems with -which 
the engineer has to deal Before entering on it, I thought 
it desirable to explain certain operations in Hydrology, in 
order to enable the student of Engineering to follow with 
more advantage the succeeding chapters. These expla- 
nations refer chiefly to the method of mafcing tidal obser- 
vations, and ascertaining the discharge of streams. 

All rivers on their passage to the sea through tidal 
channels and estuaries, assume certain recognisable and 
widely different physical features, the characteristics and 
boundaries of which I have defined. These boundaries 
divide rivers into what, for our present purpose, may 
perhaps conveniently be termed ertgineering compart- 
menta ; and I have explained the varied works which are 
applicable to each of them, and shown their effects by 
describing different navigations where th^ have been 
succee^iUy adopted. 

The concluding chapters are chiefly devoted to the 
origin of " Bars," the effect of " Backwater," and the 
Beclamation and Conservation of Land. 

It seems to me that such branches of Engineering 
may be most usefully discussed by explaining general 
principles, — describing works designed to produce certain 
effects, — showing their application in practice, and record- 
ing results. This is the plan I have endeavoured to 
follow, and accordingly every statement of principle has 



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been illuetrated by at least one example in practice. 
Where my own experience fiiiled to surest examples, I 
had no difficulty in applying to my professional brethren, 
and I have great satis&ction in acknowledging the friendly 
interest they took in assisting me to carry out the object 
I had in view. 

It will thus be found that the foUowing pages contain 
a rSmmS of a pretty wide field of research, which I 
trust may prove in some respects useAil, if not to the 
engineer in his practice, at leaat to the pupil in the 
study of his profession. 



Bdikbuboh, April 1ST2. 



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CONTEXTS. 



CHAPTER I. 

E&ROB CAXAI& 

Early iaiiawj of Bug* e 

Fon Dyke and Cmt Dyke Cuala— Btidgewator ud otbw Cuab— 
g eaily eiaah Ctnwi l priodpln id eaaal 
rata^-Sectkwal ana— KracbM and kicka— 
Tnplmiwl plinn a&d p^pendicnlar liftfr-^Mooklaikd Caaal inrTino 
WaMte w»i»— Stay-gato— Off-la * i Drainaga a£ towpatba—Poddl*— 
Mode of eandactiDg traffio — Wiatiiig c^ tlm banka — Steam-towing oo 
OlotuMto' and other eanala — Steam-towing on rJTera, 



CHAPTER II, 

SHIP CANAU, 

Utility of Ship eanala — Langnedoc, Forth and Clyde, aad Criuaa Caaali 
— Ship oauali divided into three claaaea : thoae through high diatriota 
of connby ; those throngh low-lying diabicta ; and thoae without 
locka, doiving their water-anpply from the tea — Caledonian Canal — 
(^nala of Iforth HoUuid — AmBterdam Canal — Snea Canal, 



CHAPTER III. 

THE COUPABTHENTS OF BIVEBS DEFINED. 

Compattmenti of riren — Tbar phyncal charaoteiiatica deaoribed — Ex- 
ample of Dornoch firth — Bonndariet of compaitmenta not alwaya 



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diHtiiict — DifTeient compartments require dUtinct engineoing work* 
for their improTement, 



CHAPTER IV. 

HYDROMETRIC OBSERVATIONa 

Tides of riTSTB— VariatioDi in the tidfti liaee — Proteisor Robison's remwka 
on the anomiliea of nver tides — Nature of the inquiry into river tides 
— Tide-gaogM — Selection of stations for tide obsorrations — Agents 
which produce dislnrbance in the parallelism of the tidal lines — 
Manner in which these variations affect the soundinga — Datam line for 
iwondings — Use of tide-gauges in reducing soundings to the datnm — 
Formulie for their reduction— Formulw only true on the snpposition of 
the lines being parallel to high water — Besults affected by erroneoos 
snppoaitton — Most effectual means of avoiding inaccuracy ; but thia 
not always practicable— General rales for taking soundings — High 
and low water sonnding» — Formnln for aacertaining the rise of tide 
and height of sand -banks — Cross sections — Bnlefor determining eleva- 
tions along a tidal river without levelling ; not applicable to rivers 
in this coontry, .......... 



CH.A.PTEE V. 

DISCHABGE OP RIVEBS—UHDEK-CTEKENTa— SPECIFIC 
GRAVrriES OF WATER, ETC. 

Discharge of rivers — Mode of detennining the velocity of a river ; by 
floats i by tachometer — Formula for reduciug the aurface to mean 
velooity— Methods of ascertaining discharge by formnln — Formala 
generally applicable, hut affording only an approximation — Floods — 
Kscharge should be ascertained in normal condition of stream — 
Method of ganging average disohatge, exdosive of floods — Besults of 
formnlte destroyed where nnder^cnrrents exist — lostruments for ascer- 
taining nnder-cnrrents — Tachometer — TJnder-cnn-ent floats used at 
Cromarty Firth ; in deep-sea researches, etc. — Cause of nnder-cmrents 
. — Methods of obtaining specimens of water from different depths — 
Different forms of hydrophores, sud manner of using them — Occur- 
rence of fresh water in the sea — Specific gravities of fresh and salt 



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CHAPTER VI. 

THE "KIVEK PROPlk" COMPARTMENT. 

izM of riven proportioital to the Extent of oountr^ dniaed — Hie Hiub- 
■ippi an example of k Urge river — Deecnption of iti naTigatian, cut- 
renta, and diwJuu-ge — Work* propoeed for iti improvemeat — Meuu 
oMd for rendering the upper portions of tmall rirers narigable, by 
■taoehea, dams and locka — ImproTementi of npper portiona of Con- 
tinentiJ riven, moh aa the Rhine and Duinbe, 134 



CHAPTER VII. 

TIDAL PEOPAGATIOH AND TIDAL CTEBENTS OP RIVERS. 

Importance of tidal flow — Ita extent modified by circnmitanoea — Tidal 
wave — Laws of its propagation — Tidal cnrrenta — Obstaclea which 
operate in retarding tidal wave — ^Bore on the Dee — Bore on the 
Severn^ Bore on the Amazon — Level of high water not rsiaed bj 
hdlitatiTig tidal propagation, 156 

CHAPTER VIII. 
TIDAL COMPARTMENT— WORKS FOR ITS IMPROVEMENT. 



Removal of obttniotioiii to tidal flow— Wein erected for public w 

Worka for improvement of tidal compartment of riven — Itt, Removal 
of lateral obatmctioTifl ; jettiea objectionable ; piera of bridges objec- 
tionable — 2d, Training walls ; Bibble low-water baining walli ; 
comparative advantages of strught and enrved walla ; fonn and oon- 
■tmatioD of river walla — 5d, Closing of anbaidiarj' channela — tii, Snb- 
atitoting straigbt cat* for bends — BfA, Dredging ; its. introdnction ; 
bag and spoon dredge ; bncket between two lighten ; 'steam dredge* ; 
hand dredges; dredging on the Clyde and Wear; improvements in 
steam dredges; dredging on Amsterdam and Suez. Canals; longitn- 
dinal and cross dredging ; blasting at Hie Severn, and at St. Helien, 
Jersey ; dredging in exposed sitaations — tlh. Excavation ; by diving- 
bell ; by floatation ; by oofi'erdamH — lli, Sconring— 6lA, Reducing the 
inclination of the bed, 



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CHAPTER IX. 

APPLICATION OF THE8E WORKS IN PEAOTICE. 

On the Biver Tt,j : deacription of woi^a exeoated ; ahentaOD* prodnoed 
on the alopea, and ratea of propagktioD and duration of tidal influence 
— The RiTor Forth : description of worka ; their e&aot on the propaga- 
ti<m of the tide — Lawa of tidal propagation in rivera generally — The 
Biver Bibble: worka executed and their effect*— The River Lnne: 
irorka axecnted and their eSeota — The River Clyde : ita former and 
proent condition — The River Teea ; worka executed and th^ effecta. 



CHAPTER X. 

SITUATIONS WHERE THE PBISCIFLES OF IMPROVEMENT 
RECOMMENDED ARE NOT APPUCABLE, .... 



CHAPTER XI. 

WORKS FOR ACCOMMODATION OP VESSELS. 

Docka^ride-bMina — Groynea — River qnayi ; exMiiplei of those at Bel- 
fast^ Londonderry, and the Clyde^ ....... 



CHAPTER XIL 

"SEA PROPER" COMPARTMENT OP RIVERa 

Bwf ; theoriea to account for the formation of — Origin of ban, aa illua- 
trated by the Dornoch Firth ; condltiona tinder which hare are formed 
— Barleea livera— Depth over bare due to aconr— Effect of river and 
tidtJ water in eatnariea — Backwater ; ita importance for aconring ; 
diflerent aapecti under which backwater may be viewed, aa illuatnted 
by Hartiepool alakc^ Moatroae baain, and WftUaaey Pool — Level at 
whioh baokwator is abatraoted— General propodtions regarding back- 
water — Lower parte of wtuariea, auch aa the Meiaey, etc., caimot be 
improved unleaa at great cost — Ban of auch riveta aa the Tyoe and 
Wear may be improved by protecting piera — Bar of the Mimiawirpi— 
Bar of the Danube ; it* canse, and work* for ita improvement — Hard 
bars — Qroynea, 



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CHAPTER XIII. 

BECLAMATION AND PKOTBCTION OF LAUD. 

Sohames for gaining land uid improving luTigktiou lomBtitiies not omn- 
t>*tiUe — niiutntod hy the D«»-~I>epreMion of low-water line aipt to 
mialead, aa teatad in the Lnne — Increate of tidal water at Hm Luim, 
Tay, and Bibble, and its effect ai a iconring agent — Adjoming pro- 
pertf benefited hj lirer intprovementB — Proceai of land-making de- 
pends on aaMnnt of mattan held in tnapeaaion— HsBneat mattara 
fonnd next the aea in tidal wtuarie* ; the rerene in inch riren aa the 
Dannbe, etc — Sise of partiolea which cnrrenta are capable of carrying 
— Weight of different deporita in the bed of the Clyde — Quanti^ of 
matter held in •oapeoaion by different rivers — FormatioD of deltas — 
Lerel of T^^etatioD on manh landa — Work* for protection of maiah 
lands — Works for protection of land in open ertnariea. 



CHAPTER XIV. 
CEOSSINa OF NAVIGATIONa BY RAILWAV BRIDGES, 



PHYSICAL CHARACTERISTICS OF HTVERS, . 
raoEX, 



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LIST OF PLATES. 

1. CALBDONIAS CANAL— Plas akd SEcnoir, . Tc 

n. AUSTERDAU CANAL~Pt.Air akd SlccmOH, . . , 

in. SUEZ CANAL— PiAH amd Sbcthmt, ... 

rV. DOEKOCH FIRTH— Ckasi at Eivsii, ... 

V. CHABT OF THE DEE, 

VL DIAGRAM OP TIDAL LIKES OP THE DEB DUEIMO 

THE FLOOD OF A SPRINO TIDE, ... 
VII. DO. DO. DURIHO AN EBB TIDE, 

VIIL CHAET OP THE LUNE 

12. DIAGRAM OP TIDAL LINES OF THE LUHE DURING 

THE FLOOD OF A SPRING TIDE. ... 
X. DO. DO. DURING AN EBB TIDE, ... 
XL DIAGRAM SHOWING TIDAL LINES OP THE DEE 

DURING THE EBB OF A NEAP TIDE, . 

XII DIAGRAM SHOWraO TIDAL LINES OF THE LUNE 

DOBING THE FLOOD OF A NEAP TIDE, 

Xm. DIAGRAM SHOWING TIDAL LINES OF THE RIVER 

FORTH, 

XIV. CHABT OP THE RIVER TAY, 
XV. CHART OP THE RIVER RIBBLE, ... , 
XVL ELEVATION AND PLAN OP ODSE HTDRAULIC 
SWING BRIDGE, 



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INLAND NAVIGATION. 



CHAPTER I. 

BABQE CANAIA 



Eufyhiitoiyof B«rge ouuli— Invoitioa of locka— lAngaedoa Cuul — PouDyka 
■ndCMirDjke Canals — Bridgewater and otber Canali — Difficnltde* in ocmatonot- 
ing early canal* — OenemI prmriplM of canal coiutrnctioti — Supply of water 
— Sectional area — Seachea and locka — Inclined plane* and perpeodicnlM' lifta 
— Honklaud Canal inoline — Waits weira — Stop-gatea — Off-leta — Drainage of 
totrpatlu — Puddle — Mode of cooduotiDg baffio — Waiting of Uie bamka — 
Steam-towing on Oloncetter and other canal* — Steam-towing un riven. 

That railways have entirely superseded, and will iiiEaiijUitoiToi 
iiiture prevent, the extension of canal or water carriage 
as a means of ordinary transport, must at once be con- 
ceded. The days of the bargemen baiting their horses at 
eveiy stage, and travelling from town to town and from 
village to village at three miles an hour, are ended, and 
the change is not to be r^retted. The great objections 
to relying on canals for keeping up r^ular internal com- 
munication are their liability to stoppage from a deficient 
supply of water during dry seasons, the interruption to 
which they are e:sposed from ice during winter, and, 
especially, in these days of express railway trains and 
electric tel^^raphs, the veiy limited speed at which the 
canal-boats can be propelled. Sir John Kennie, some 
twenty years ago, in speaking of the successful attempts 



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2 inulnd navigation. 

made to iniroduce swift boats, and the great improvement 
that was thereby effected in canal transport, says, — " All 
this, however, came too late ; for although it woidd have 
been readily acknowledged at an earlier period, and might 
perhaps, for a while, have retarded the railway system, 
yet when once the latter was established, its superiority 
became manifest, and its progress irresistible."' To 
modem travellers the old canal track-boat, as compared 
to the railway train, seems to have got so completely out 
of date, that it may at first sight be considered as imcalled 
for to describe, even briefly, a class of works which may 
almost be regarded as obsolete. It appears to me, how- 
ever, that the simple consideration of the great antiquity 
of navigable canals, their wide-spread introduction through- 
out the world, the important place which they have so 
long occupied in the commercial history of eveiy country, 
and, above all, the noble specimens which they afford of 
hydraulic engineering of a confessedly difficult nature, 
executed at a period when the mechamcal appliances of 
modem tiroes were unknown, g^ve to such works an im- 
portant place in the history of Inland Navigation. 

From the writings of Herodotus, Aristotle, Pliny, and 
other ancient historians, we learn that canals existed in 
Egypt before the Christian era, and there is reason to 
believe that at the same early period artificial inland 
navigation had also been introduced into China. Almost 
nothing, however, save their existence, has been recorded 
with reference to these veiy early works ; but soon after 
the commencement of the Christian era canals were Intro* 

^ MtmUtu^ Proetmengi qf Itulilvtkm <tf Gvii gnginetn, vol. v. p. 78. 



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BAIU3E CALAIS. 3 

.duced, and gradually extended throughout Europe, in 
Italy, Spain, Russia, Sweden, Holland; and France.^ 

In speaking, however, of the earliest of these works, 
it is not to be supposed that they resemhled the modem 
canals constructed in our own and other coimtries. It was 
not until the inrentjon of canal-locks, by which boats could 
be transferred from one level to another, that inland navi- innntion of 
gation was rendered generally applicable and useful; and it 
has been truly remarked, " that to us, living in an age of 
ateam-enginea and daguerreotypes, it might appear strange 
that an invention so ^mple in itself as the canal-lock, and 
foimded on properties of fluids little recondite, should 
have escaped the acuteness of 'Egypt, Greece, and Bom&"* 
Not only, however, had the invention escaped the notice 
of the ancients, but what is more striking, the several 
gradations made towards the attainment of that simple 
but valuable improvement appear to have been so gradual, 
that, like many discoveries of importance, great doubts 
e^dst as to the person and even the nation by whom 
canal-locks were first introduced. One class of writers 
attributes the discovery to the Dutch ; and Messrs. Tel- 
ford and Nimmo, who wrote the article on Inland Navi- 
gation in Brewster's Edinburgh EncyclopcBdia, adopt the 
conclusion that locks were used in Holland nearly a 
century before their application in Italy ; while, on the 
other hand, tbe invention has been strongly and not 
unreasonably claimed for engineers of the Italian school, 

• Fulton on CtuuJ NiTigation,- London, 1796 j Vallancey'i Trtaliit m Inkmd 
IfaOffiaiim, Dnblin, 1763 ; TaUuun'a Political Economy of Inland Na.vioalii», 
I^mdoD, 17M ; " Inbnd NkTigation," Brswiter'B Bdinburgh Sncfdcpadia. 

» Qutrleiif BeiHew, No, cilTi, "N»Tig»We Ctuuli," by P«nl FruL 



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* INLAND NAVIOATION. 

and, in particular, for Leonardo da Yinci, the celebrated 
engineer and painter.' Without, however, entering into a 
discussion of this question, which it is now perhaps 
impossible to aolve, we may safely state, that during the 
fourteenth century the introduction of locks, whether of 
Dutch or Italian origin, gave a new character to inland 
navigation, and laid the basis of its rapid and successful 
extension. And here it may be proper to remark, that 
the early canals of China and Egypt, although destitute 
of locks, do not appear to have been on that account 
formed on a imiform level unadapted to varying heighta 
I do not know that the use of locks has even yet been 
introduced into China, intersected as it is by many 
canals of great antiquity and extent ;' and in order to 
pass boats from one level to another, the Chinese have, 
from a very early period, employed stop-gates and in- 
clined planes of rude construction. Nevertheless, the 
invention of locks was, aa already noticed, a most impor- 
tant step in the history of canals; and that mode of 
surmounting elevations may be said to be almost univer- 
sally adopted throughout Europe and America. Inclined 
planes and perpendicular lifts have, it is true, been em- 
ployed in these countries, as will be noticed hereafter; 
but the instances of their application are undoubtedly 
rare. 

But without tracing the gradual introduction of canals 

- from countiy to country, I remark at once, that we find 

the French, at the end of the seventeenth century, in 

> Frin OD Nftvigable CaDil^ p. 154. 

* Tha Impeiul CaD>l in China u said to be apiraids of 1000 nilea in length. 



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BABOE CAKAIB. 5 

the reign of Louis xiv., forming the Languedoc Canal, 
hetween the Baj of Biscaj and the Mediterranean, a 
gigantic work, which was finished in 1681. It ia 148 
miles in length, and the summit-level is 600 feet above 
the sea; while the works on its line embrace up- 
wards of one himdred locks and about fifty aque- 
ducts, — the whole forming an imdertaking which is a 
lasting monument of the skill and enterprise of its pro- 
jectors ; and with this work as a model, it seems strange 
that Britain should not, till nearly a century after its com- 
pletion, have engaged in vigorously following so laudable 
an example. But this indeed is aU tbe more extraordi- 
nary, seeing that tiie Romans in early times had executed 
works in England, which, whatever might have been th^ 
original use, whether for the purposes erf" navigation or 
drainage, were ultimately, and that even at an early 
period, converted into navigable canals. Of these works 
I particularly specify the Caer Dyke and Foss Dyke cuts 
in Lincolnshire, which are by general consent admitted to 
have been of Bomau origin. The former extends firom 
Peterborough to the river "Witham, near the city of 
Lincoln, a distance of about 40 miles ; and the latter 
extends from Lincoln to the river Trent, near Torksey, a 
distance of II miles. 

Of the Caer Dyke the name only now remains, but the 
Foes Dyke, though of Roman origin, still exists, and, as it fom Drke 
is the oldegt British canal, the reader may be interested 
to learn the following iacts as to its history, which I 
gathered some years ago, when designing works for 
its improvement. Camden in his Sritcmnia states that 



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6 INLAND NAVIGATION. 

the Fobs Dyke was a cut originally made by the 
Romans, probably for water-supply or drainage, and 
that it was deepened and rendered in some measure 
navigable in the year 1121, by Heniy L In 1762 it was 
reported on by Smeaton and Grundy, who found the depth 
at that time to be about 2 feet 8 inches.' They, how- 
ever, discouraged the idea of deepening it by excavation. 
They say they found " the bottom to be either a rotten 
peat earth, or dse a running sand," and that though the 
deepening of the navigation is in " nature possible," yet 
it " cannot be effected without removing one of the banis, 
in order to widen the same," which woidd not only turn 
out expensive, hut would " occasion much loss of time 
and profit to the proprietor, while the work is executing." 
Nothing followed on this report, hut in 1782 Smeaton 
was again called in, and deepened the navigation to 3 feet 
6 inches, not, however, by widening the canal or dredging, 
but by raising the water-level 10 inches.* From that 
period nothing more, was done to enlarge iAie water-way, 
or adapt it to increased traffic Meantime, however, 
the adjoining Witham navigation, having been im- 
proved, the defects of old Foss became more apparent, 
and in 1838 Mr. Vignoles was consulted, and made an 
elaborate report on alternative schemes for increasing the 
depth to 4 and 6 feet ; nothing, however, was done till 
1840, when Messrs. Stevenson of Edinburgh were em- 
ployed to design works for assimilating the Fobs Dyke, as 
for as practicable, both as regards width and depth, to the 
navigable channel of the Witham. On examination I 

> Smeaton's SeporU, to). I p. Cfi : Landoii, 1812. ■ Ibid. p. 74. 



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BA£GE CANAI£. 7 

foxmd the depth of the Foes to be 3 feet 10 inches, anA 
its breadth in many places was insufficient to admit of 
two boata passiDg each other, and for their conTenience 
occasional passing places had been provided. It was 
resolved to increase the dimensions of the canal, and to 
repair the whole work. Accordingly it was widened to 
the minimum breadth of 45 feet, and deepened to t^e 
extent of 6 feet throughout ; alterations which were ac- 
complished, without stopjung t^e traffic, by using steam 
and hand dredges, speeiaDy designed for the purpose. 
The entrance-loci, communicating with the river Trent 
at Torksey, was renewed, and a pumping -engine was 
erected for supplying water firom the Trent during dry 
seasons, and thus that ancient canal, which is quoted by 
Telford and Nimmo as "the oldest artificial canal in 
Britain," was restored to a state of perfect efficiency at a 
cost of about £40,000, forming an important connecting 



Fio. 1. 

link between the Trent and Witham navigations. Fig. 1, 
which is a cross section at a place called " tlie Narrows," 
shows the former bed and banks in dotted lines, imd the 
hard lines show the dimensions to which the canal was 
increased. 

Notwithstanding the existence of this early work, 
however, and of some others in the coxmtry, particularly 



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8 INLAND NAVIGATION. 

tJie Sankey Brook Navigation, opened in 1760, it cannot 
be doulited that the formation of the Bridgewater Canal 
in Lancashire, the Act for which was obtained in 1759, 
was the commencement of British Canal Navigation ; and 
that FranciB Duke of Bridgewater, and Brindley the 
engineer, who were its projectors, were the first to give 
a practical impulse to a class of works which, under the 
" guidance mainly of Smeaton, Watt, Jessop, Nimmo, 
Rennie, and Telford, has been very genially adopted 
throughout the country, and has undoubtedly been of 
vast importance in promoting its commercial prosperity.' 

According to Mr. Smiles, the barge canals laid out by 
Brindley, although not all executed Irjr him, were :* — 

Milra. 
The Buko's Canal, Longford Bridge to Runcorn, 21 
Worsley to Manchester, . . .10 

Grand Trunk, &om Wilden Ferry to Preaton 

Brook, 
Wolverhampton, 
Coventry, 
Birmingham, 
Dioitwich, 
Oxford, . 
Cheeterfield, 



It is believed that the length of these inland boat- 
navigations, constructed in Britain, exceeds 4700 miles. 

Many of them w«re carried at great cost throu^ hilla 
and over valleys. The Harecastle tunnel on the Grand 

> Nittory <^ Inkatd Navigation, putionlarly tUoM of the Duke of Bridge- 
vater, Loodon, 1786 ; Hughei't Memoir of Brindley, Weals'* Quarterly Paper*, 
LoDdon, 1M3. 

> Smilea's InBt* nf Ike Snginetrt. 



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BABGE CANAI& 9 

Trunk Canal, made by Brindley, and afterwards doubled 
by Telford, is nearly one and a half mile in length ; and 
the Pont-y-pyssylte aqueduct, on the Ellesmere Canal, 
over the Dee, constructed by Telford at a coat of £47,000, 
has nineteen openings, 45 feet span, and is elevated 126 
feet above the river, the canal being carried across in a 
cast-iron trough.' 

It must be obvious that, to construct a navigable chan- iwBenitiM in 
nel through a country varying in level, and affording per- 1 
haps no great &cilities for obtaining a supply of water, 
infers high engineering skill. Yast reservoirs must in 
some cases be formed for stoiing the water necessaiy to 
supply during diy seasons the loss by lockage, leaki^, 
and evaporation. Feeders must be made to lead this 
water to the canal ; hUls must be pierced hy tunnels ; 
valleys must be crossed on lofty embankments, or spanned 
by spacious aqueducts ; and, above all, the whole must be 
conceived and laid out with soiipulous regard to the all- 
important object of securing the works against injury from 
an overflow of water dming floods, and a consequent inunda- 
tion of the surrounding country. Moreover, the necessity 
of laying out the caual in level stret<^es, and surmounting 
elevations by means of locks or inclined planes, occurring 
at intervals, often occadons much difficulty, and greatly 
restricts the resources of the engineer. Taking, then, all 
these circumstances into consideration, and bearing in 
mind that canals were the pioneers of railways, we t.hinlr 
it may safely be affirmed that the canal engineers of 
former days had much more serious physiccU difficulties 
1 Hfis qf Ttifi>ni, London, 183S. 



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10 INLAND NAVIGATION. 

to contend with than are experienced in cariTuig out the 
railways of modem timea ; if we except such works as the 
Britannia Bridge, the high-level bridge of Newcastle, the 
Boxhill Tunnel, and some other kindred works. But, 
indeed, their mechanical difBcultiea were also greater; 
for the introduction of steam, and its wide-spread appli- 
cation to all engineering operations, affords fitcilities to 
the engineers of the present day which Smeaton at the 
Eddystone, Stevenson at the Bell Bock, and Kennie and 
Telford in their early navigation works, did not enjoy. 
The distinguished merits of the engineers who practised 
in the former, and at the commencement of the present 
century, cannot indeed be over-estimated; and had it been 
within the scope of this treatise I should readily, because 
I am sura profitably, have described in detail some of the 
grand aqueducts and other works on the lines of our 
canala All I can do, however, consistently with the 
limits to which I have restricted myself, is to indicate iiie 
general principles which should guide the engineer in 
selecting the route for a canal, referring for details of 
construction to treatises on the Strength of Materials, 
Bridge-building, Tunnelling, Earthwork, Masonry, Carpen- 
try, and Reservoirs, all of which are more or less applicable 
to the formation of canals ; and perhaps the best reference 
to books on these various subjects is to be found in Pro- 
fessor Bankine's valuable Manual of Civil Engineering. 

I shall only therefore offer to the student the follow- 
ing summary of engineering principles, generally applicable 
to all cases. 

A canal cannot be properly worked without a full sup- 



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BABOE CAKAI^. II 

ply of water, caloilated to last over the driest season of supply or 
the year, and in that respect, exoept as to the quality of 
the water, demands all the care and attention requisite in 
investigating the sources of water for supplying towns. 
If there be no natural lake in the district available for 
supplying the canal, and affording storage for dry seasons, 
the engioeer must select such situations as are suitable 
for the construction of artificial reservoirs, and the condi- 
tions to be attended to in selecting th^ positions are the 
same as those for water-works. They must command a 
sufficient area of drainage to supply the loss by leakage, 
evaporation, and lockage, due to the length of ihe canal, 
the number and size of the locks, and the probable amount 
of traffic. The capability of the district to afibrd this 
supply will depend on the area of the watershed, and the 
annual amount of niin-&U, as ascertained by accurate 
rain-gauge observations. The off-lets from the reservoirs 
must be at such an elevation as to admit of water being 
conveyed to the summit-level of the canal The embank- 
ments for retaining the water must be erected on sites- 
affording a &vouralde foundation, and so situated, with 
reference to the valley above them, that they shall, with 
the mimmum height and length of embankment, dam up 
the maximum amount of water. It is further necessary 
to consider whether the subsoil of the vaUey forming the 
reservoirs is throughout of so retentive a nature as to 
prevent leakage ; and it is also essential to provide, by 
means of waste wfoxs, for the dischai^ of floods. The 
Caledonian Canal, to be afterwards noticed, is, in this 
respect, very favourably situated, ihe whole supply being 



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12 INLAND NAVIGATION. 

obtained from natural lochs. In other cases, such as the 
Union, Forth and Clyde, Crinan, Birmingham, and other 
canals, it has been found necessaiy to construct large 
artifidal reserroirB, firom which the water is led in feeders 
to points convenient for forming a junction with the 
canaL The water in these reservoirs is stored up in 
winter, and let oflf as required during the droxjghts of 
summer. In situations where the canal communicateB 
with the sea or a tidal river, and where the natural sup- 
ply is small, as at the Foss Dyke, already referred to, the 
water is raised by pumping enginea 
8«ctioiiai iTM. The sectional area of the barge canals constructed in 
this country are between 4 and 5 feet in depth. When 
the soil in which they were made was retentive, tiiey 



were formed as shown in the cross section, fig. 2. But 
when the soil was porous, clay-puddle was introduced, as 
shown in fig. 3. Professor Rankine says the depth of 



water and sectional area of water-way should be such as 
not to cause any material increase of the resistance to 
the motion of the boat beyond what it would encounter 
in open water, and ^ves the following rules as fiilfilliDg 
these conditions : — ■ 



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BAItOE CANAU. T3 

Least breadth at bottom, =a 2 x gi'eatest breadth of boat. 
Least depth of water, = I i foot + greatest draught of boat. 
Least area of water-way, = 6 x greateat midship section of boat. 

In laying out a line of canal, the engineer is much more vmcbM 
restricted than in fixing the route of a road or railway, 
where gradients more or less gentle can he introduced to 
suit the undulating aur&ce of the country. A canal, on 
the contrary, must foUow rigidly the hases of sloping 
hills, and the windings of valleya, so as to preserve a 
imiform level, and it is of great importance to lay out the 
work in long reaches, on the same level, and to overcome 
elevations in cumulo, by means of locks at places where 
the nature of the country admits of its being most advan- 
tf^eously effected. This not only leads to a saving of 
attendance and expense in. working the canal, but is also 
more convenient, aa presenting fewer stoppages to the 
tra£Sc ; but, according to Professor Rankine, single locks 
are more fevourable than flights of locks to economy of 
water. The means of overcoming the difference of level 
between the various reaches must depend very much on 
circumstances. "With few exceptions, the change of level 
is effected by means of locks, which generally have a lift 
of 8 or 10 feet, though in some cases it is somewhat 
greats. The dimensions of the locks ought to be regu- 
lated by the traffic; but they should, in order to save 
water, be as nearly as possible the size of the craft to be 
passed through them, allowing about a foot of extra 
breadth and draught of water. The barge canals of which 
I am speaking have locks about 8 feet in breadth, and 
from 70 to 80 feet long, and their use in raising or lower- 



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14 INLAND NAVIGATION, 

ing boats from the different reaches are so well knowu as 
not to require explanation. 

The water is generally admitted into and flows from 
each lock by sluices formed in the gates. Sir William 
Oubitt, in carrying out the improvements of the Severn 
navigation, introduced the water through a culvert 
parallel to the side wall of the lock, and opening in the 
centre l^ means of a tunnel, which admits 16,000 cubic 
feet of water to flow into or out of the lock in 1^ minute ; 
and in httle more than that time loaded vessels can be 
< passed through.' Inclined planes and perpendicular 
lifte, which have the great advantage of saving water, 
have also been adopted so long ago as 1789 on the 
Eetling Canal in Shropshire, and aftervmrds on the 
Duke of Bridgewater's Canal. The most extensive ap- 
plication of inclined-plane navigation which I have seen, 
is that of the Morris Canal in the United States, 
constructed by Mr. Douglas of New York, on which 
there were no fewer than twenty-three inclined planes, 
having gradients of about 1 in 10, with an average lift 
of 58 feet. The boats weighed, when loaded, 50 tons, 
and after being grounded on a carriage, were raised by 
water-power up the inclines with great ease and expedi- 
tion. The length of the Morris Canal, between the rivers 
Hudson and Delaware, is 101 miles, and the whole rise 
and fall is 1557 feet, of which 223 are overcome by locks, 
and the remaining 1334 by inclined planes.' When first 
describing this work in my book on American Engineer- 

' Miimttt of Proceedingt qf Itutitvtitm of Civil Enghieert, toL t. p. 340. 
■ Ste*ciiMiu*a SieUh t^ Civil Engiiuering in North Amtriac. 



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BARGE CAKAU. IS 

ing, I stated that the principal objection to the use of in- 
clined planes for moving boats from different levels was 
the injmy they were apt to sustain in supporting great 
weights while resting on the cradle during their progress 
over the plane. A aUmlj-bmlt canal-boat 80 feet long, and 
loaded with 30 tons, could not be grounded on a smooth 
sur&ce without etiaijung h^ timbers, but this objection 
has to some extent been overcome on an inclined plane more HonUaud 
recently constructed by Mr. Leslie and Mr. Bateman on the 
Monkland Canal, where the boats are not wholly grounded 
on the carriage, but are transported over the incline in a 
caisson of boiler-plate contfunlng 2 feet of water, and are 
thus water-borne. This inclined plane is wrought by two 
high-pressure steam-engines of 25-hor8e power each. The 
height from aur&ce to surface is 96 feet, and the gradient 
is 1 in 10. The mftTrimnm weight raised is &om 70 to 80 
tons, and the whole traufiit is accomplished in about ten 
minutes. For the five yeaia previous to the end of 1856, 
the average number of boats that passed over the incline 
each year was 7500. Mx. Green introduced on the Great 
Western Canal a perpendicular lift of 46 feet. Sir WU- 
liam Cubitt has also introduced three inclined planes, 
having gradients of 1 in 8, on the Chard Canal, Somerset- 
shire. One of these inclines overcome a rise of 86 feet ; 
and they are said to act very satisfectorily.^ 

An essential adjimct to a canal is a sufficient num-wutawdn 
her of waste weirs to admit of the discharge of the sur- 
plus water which accimiulates during floods, and which 
may, if not provided with an exit, rise to such a height as 

' MitutU» of Proeteilaigt of Jmtittrfion of CiiM Engintm, ToL xiii. p. 2U5. 



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16 INLAND NAVIGATION. 

to overflow the towpath, and cauae a breach in the banks, 
producing stoppage of the traffic and damage to the ad- 
joining lands. In determining the number and positions 
of these waste weirs, the engines must be guided entirely 
by the nature of the country through which the canal 
passes. Whenever an opportunity occurs of discharging 
surplus water from an aqueduct into a stream crossed by 
the canal, a waste weir may safely be introduced ; but, 
independently of this natural facility, the engineer must 
consider from what quarters, and at what points, the 
greatest influx of water may be apprehended, and roust 
at such places not only form waste weirs of sufBcient size 
to let off the surplus, but prepare artificial courses for its 
dischai^ into the nearest streams. These waste weirs 
are overflows placed at the top water-level of the cfmal, 
so that in the event of a flood occurring, the water flows 
over them, and thus relieves the banka The want of 
sufficient escape for flood-water has occaaoned overflows 
of canal banks which were attended with very serious 
injury to the works, and lengthened suspension of the 
traffic ; and attention to this particular part of cfmal con- 
struction is of essential importance. 

It is necessary to introduce stop-gates at short inter- 
vals of a few miles, for the purpose of dividing the canal 
into isolated reaches, so that in the event of a breach 
occurring, the gates may be shut, and the discharge of 
water confined to the small reach intercepted between two 
of them, instead of extending throughout the whole line 
of canal. In latge works these stop-gates may be most 
advantageously formed in the same manner as the gates 



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BABOS CANAU. 17 

of locks, two pura of gatee being made to Bhnt in opposito 
directions. In small works thej may be made of thick 
planks, which are slipped into grooves fonaed at those 
naiTow parts of the canal which occur under road bridges, 
or at contractions made at intermediate points to receive 
them. Self-acting stop-gates have been tried, but their 
success has not been such as to lead to their general in- 
troduction. Stop-gates are further found to be very useful 
in cases of repairs, as they admit of the water being 
run off from a short reach, when the repairs can be made, 
and tiie water afterwards restored, with comparatively 
little interruption to the traffia Their v^ue in obviating 
serious accidents was well exemplified on one occasion ia 
my own experience. The water during a heavy flood 
flowed over the towing-path of the Union Canal connect- 
ing Edinburgh and Glasgow, near the end of an aqueduct 
which adjoined a high embankment, and the uncontrolled 
current carried away the embankment and the soil on which 
it rested, to* the depth of eighty feet, as measured from 
the top water-level The stop-gates were, on the occa- 
sion referred to, promptly applied, and the discharge con- 
fined to a short reach of a few miles, otherwise the injury 
(which was, even in its modified form, very considerable) 
would have been enormous, not only to the canal works, 
but to the adjoining lands. 

For '^e purpose of draining off the water to admit ofr-i«u. 
of repairs after the stop-gates have been dosed, it is 
proper to introduce, at convenient situations, a series 
of eiitB called " off-lets," which are pipes placed at the 
level of the bottom of the canal, and fitted with sluices 



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18 



INLAND NAVIGATION. 



wliich can be opeued and shut when tequired. These 
off-lets are generally formed at aqueducts or bridges cross- 
ing rivera where the contents of the canal can be run off 
into the bed of the stream, the atop-gatea on either 
side being closed, so as to isolate the part of the canal 
from which the water is withdrawn. 

In executing the work, provision must be made for 
the proper drainage of the towpath, which should be 
made highest at the side nezt the canal, and sloped with 
a gentle inclination towards the outside. The drainage 
of the towpath should be carried to a sky drain, and at 
intervals passed below it into the canal, as shown in fig. 4. 



The preservation of the banks at the water-line is also 
a matter of importance. " Pitching" with stones and 
" facing" with brushwood are employed, and, in my ex- 
perience, the latter, if well executed, forms an economical 
and effectual protection. Fig. 4 is a section of these works 
as executed at the Foas Dyke. 

In forming the alveus or bed of the canal, great care 
must be taken, e^>ecially on embankments, and even in 
cuttings, where the soil is porous, to provide against 
leakage l^ using puddle, as shown on fig. 3, page 12. 
And here it is proper to remark, that an all-important 



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BABGB CANAIB. 19 

matter, as affecting the oonstructioii of the works, is the 
possibility of getting day in the district, or such other 
soil as may be worked into puddle, on the good quality 
of which the stability of the reservoir embankmenta, and 
the imperviousness of the beds and banks of the canal, 
mainly depend. 

These are the only points of general application, in the 
construction of canals, to which I can advantageously 
refer ; and in applying them to each case, the student 
must be guided, Jirst, by theoretical knowledge, to be 
acquired by a careful study of his profession ; and, 
secondly, by that experience which can be gained only 
by attendance on works in actual operation. 

The best mode of conducting traffic on canals and Mode of om 
lirers is hardly within the limits of this treatise, seeing on cuuia. 
that it is a subject not directly connected with the 
construction of canals or the improvemrait of rivers, but 
rather with the use made of them after having been con- 
structed or improved. 

Not a httle, however, has been written on the subject, 
and I refer the reader who wishes to study it fully, to the 
observations made by Mr. Walker and Mr. (Jeoige Kennie, 
in the Transactions of the Royal Society and of the Institu- 
tion of Civil Engineers, and especially to the very valuable 
researches on hydrodynamics by Mr. J. Scott Russell, in 
the Transactions of the Royal Society of Ediiiburgh. 

These investigations were made before the general 
establishment of railways, at a time when svn& canal 
travelling seemed still a desirable attainment, and no- 
thing can be more interesting than Mr. Kussell's able 



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20 INLAMD NAVIGATION. 

treatment of that subject But though bocUs propelled 
at high speed on canala have g^ven place to railway 
carriages, yet the canal traffic must be conducted, and 
the cheapest means of Meeting the " haulage" mth the 
least danger to the banks is stilt an important inquiry, 
and has -within the last few years afforded matter for 
some highly interesting papers and statements in the 
Proceedinga of^ Institution of Civil Engineera. These 
are communications on the employment of steam power 
on the Gloucester and Berkeley Canal, by Mr. W. R 
CSegram ; on the Grand Canal, Ireland, by Mr. Healy ; 
on the Forth and Clyde, by Mr. J. Milne ; and on the 
Aire and Calder, by Mr. W. H. Bartholomew, to all of 
which I refer as containing valuable information.^ 
a One of the great objections to high speeds on narrow 
channels is the wasting of the banks by the displacement 
produced in propelling the vessel through the water. The 
wasting indeed takee place even with very low speeds, and 
as a matter of canal engineering it is necessary to notice it. 
To give an instance of the effect on the large scale : Mr. Ure 
says that the nver-steamers on the Clyde, going at a speed 
of eight to nine miles per hour, produce a swell which com- 
mences to rise when the vessel is " two or three miles off" 
— a circumstance which was first noticed by Mr. J, Scott 
BuBSell in 1837. The swell gradually increases as the 
steamer approaches, and at last, becoming a wave of trans- 
lation, it breaks on the river walls nearly abreast of the ves- 
sel, following hffl- on her coinse along the river, as a violent 
breaking wave, measuring sometimee 8 or 10 feet from the 

* Mltu^et qf Proo«tdmff» (if In^uUon <tf OivU Eagiitttn, toL zivi. p. 1. 



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BABOB GANAI^. 21 

hollow in the channel to the crest on the wall A coat- 
ing of heavy whinstone rock, from 2 to 3 feet thick, ex- 
tending from low to high water mark, is found necessarj- 
to enable the banks to withstand it. Mr. tire also found 
that the action of passing steamers, though very destruc- 
tive to the banks, was useful in stirring up the mud from 
the bottom, which was carried o£f by the currents to an 
extent which he estimates to be from 20 to 25 per cent, 
of the whole quuitity dredged from one particular part of 
the river where he carefully measured it. It will at onoe 
be apparent, that however inconvenient these wasting 
waves may be in a river, the waves in a canal, though 
smaller, are nevertheless a source of greater anxiety, act- 
ing as they do in a narrow artificial channel formed at 
some placee on high embankments, the &ilure of which 
might be attended with sotious consequencea 

The wasting on canals where the tiBfSc is conducted 
at a moderate speed is found to extend not more than 
18 inches to 2 feet, that is, 1 foot above and below the 
water-line, and Mr. Clegram states that he has found on 
the Gloucester Canal that a &cing of stone filled into a 
recess cut in the banks formed a complete protection. 
The stone &cing is about a foot in thickness, and is 
formed of stones from 18 to 20 cubic feet. The protec- 
tion adopted at the Foss Dyke Canal consisted of fescines 
of brushwood, as shown on page 18, and was found to be 
most effective. 

What has lately led to the considerataon of the best steun-towiiig 
means of protecting the banks of canals is the substitu- u>dothar 
tion of steam for horse power in working the traffic, and 



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INLAITO NAVIGATION. 



this has been entirely successful. The first attempt at 
using steam-power on canals was made on the Forth and 
Clyde Canal with Symington's boat in 1789. Mr. Milne 
states the results of various esperiments to introduce 
tugs, but these were ultimately abandoned in fiivour of 
steam-lighters, which now in great numbers navigate the 
canal, and make passages to Leith, Greenock, and other 
trading ports on the Firths of Forth and Clyde. 

This system, however, would not suit the trade of the 
Gloucester Canal, which is diiefly frequented by sea- 
borne vessels, and Mr. degram, its engineer, ^ves an 
interesting account of the introduction of steam-towing 
on that navigation. The following extracts from his 
paper seem generally applicable to all navigations where 
towing is to be adopted. He says the navigation is a 
ship canal leading fi-om the Severn at Gloucester to the 
Severn at Sharpness Point. It is 16^ miles in lengUi, 
and has a depth of water varying, according to the season, 
from 18 feet to 18 feet 6 inches. Vessels up to 600 tons 
and 700 tons raster navigate the canal to Gloucester. 
Prior to the year 1860 all seargoing vessels passing through 
were towed by horses, the number of horses being regulated 
by a scale varying from 1 horse for a vessel of 40 tons to 9 
horses for a vessel of 420 tons. The cost of this amounted 
generally to about one farthing per ton per mile on the 
register tonnage of the vessel The speed varied from I 
mile to 3 miles per hour, according to the size of the vessel 
and the state of the weather. 

In 1860 steam-tugs were placed upon the canal to 
do this work. They are iron boats, 65 feet long, 12 feet 



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BABOE CANAI& 23 

beam, and draw 6 feet 3 inches of water, fitted with high- 
pressure engines, the diameters of the cylinders are 20 
inches, with a length of stroke of 18 inches, the preesure 
of the steam being 32 lb. on the inch, and the c<et of 
each £3000. Nearly the whole of the sea-going craft are 
now towed by these tugs. The vessels range from 30 
tons up to 600 and 700 tons register, with a Tarying 
draught of water of from 6 to 16 feet. They are towed 
either singly or in a tr^, according to circumstances. 
Sometimes as many as nine, ten, and even thirteen loaded 
Teasels of from 50 to 100 tons register have been towed 
by one tug at Hie rate of 3 miles to 3-} miles an hour. 
The heaviest load drawn by any one tug has been 1690 
tens of goods, in three veaselB. Their draught of water 
varied from 14 feet 6 inches to 15 feet 6 inches, and they 
were taken the whole length of the canal at the speed of 
2 miles an hour, The smaller vessels are towed at a 
speed of 4 miles an hour, to which as a rule they are 
restricted. 

The employment of steam as a towing power has been 
found in nearly- every way advantageous. The work is 
greatly economized. The vessels rub much less against 
the sides of the banks, the power being right ahead, 
and not on one side, as with horses. The wear on 
the ropes used in tracking is much reduced, the speed 
is increased, and vessels can now be moved along the 
canal in weather which would have prevented horses 
doing the work. With a strong wind athwart the canal 
vessels cannot be tracked in train ; they must then be 
taken singly, or at most two at a time. When vessels are 



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24 INLAND NAVIGATION. 

towed in train, as a rule ihe lai^eat and heaviest dravighted 
are placed first, and the hawser leading from l^e first 
vessel to the tug, is taken fi^>m each side of the bow. 
Wil^ this arrangement, and a skilful management of the 
tug, the vessel can be kept Mrly in the line of the canal. 

The one and only disadvantage of this system, on a canal 
the sides of which are unprotected, is the additional wear 
caused by the constant passage of the tugs as well as by the 
run of crater between the sides of the large vessels and the 
banka Such vessels occupy a large part of the sectional 
area of the canal, and being taken along at a much greater 
speed than they were by horses, the back run of water is 
more rapid and prejudicial. When the vessels or trains 
of vessels are heavy, and the tugs are working up to their 
foil power and speed, the water thrown back by the 
action of the screw against the bow of the first vessel is 
thrown o£f by it to the banks on eith^ side, and is the 
cause of considerable wasL Xhis has been attempted to 
be roDaedied by placing tbe first vessel fiirther back from 
the tug ; but in practice it is found that a distance of 
from 40 to 50 feet is the farthest separation that can be 
allowed without sacrificing tiiat hold between the two 
which prevents the vessel sheering 6x)m side to sida The 
first vessel, being kept steadily in her course, the others 
foUow without much diflSculty. 

The employment of tugs has afforded an unexpected 
facility in cleansing the canal from the deposit of mud. 
Formerly it was difi&cult to remove this deposit from the 
slopes of the banka It was dangerous to apply Uie 
dredger, and although the mud in the bottom of the 



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EABOE CANALS. 25 

canal could be removed, it collected on the slopes, and at 
times mconvemently contracted the capacity of ihs canal 
Since Hie vessels hare been moved at greater speed and 
in trains, this deposit has been entirelj removed from the 
slopes to the bottom of the canal, whence it can readily 
be taken out by the dredger. 

Steam-power is even more important as connected with gi 
ttie traffic on navigable rivers, but as already stated, I do ** 
not propose to enter upon it, but must refer to treatises 
on Steam Navigation ; I shall only remark that while it 
is conducted on our narrow rivers by employing, as in 
the case of the Tees, sometimes as many as three tugs 
to take a laige iron steamer of 3000 tons from the 
shipbuilding yards of Stockton to the sea, in America 
the process is reversed, one large powerftd steamer being 
employed on the capacious rivers to tow a whole fleet of 
vessels. The towing of vesseb on the Mississippi and 
St, Iiawrence has been brought to great perfection. I 
had an opportunity of witnessing this on the St. Law- 
T0D.ce ; having passed from Quebec to Montreal in a large 
powerfbl tug-steamer, carrying goods and many hundreds 
of- passengers, and having no fewer than five sea-borne 
vessels in tow, drawing from 7 to 12 feet of water. These 
vessels were all towed by separate warps, and were ranged 
astern of each other in two lines, three of them being 
made &st to the larboard and two to the starboard ode 
of the veesel The management of a large steamer with 
so many vessels in tow, in the intricate navigation and 
strong currents of the St. Lawrence, required no small 
amount of skill ; but when it was necessary to stop the 



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26 INLAND NAVIGATION. 

steamer to take in fuel, tte eaptein dropped tte veesels 
astern and again picked them up on reeunung his course, 
with a dexterity whidi I have never seen equalled, and 
we made the passage of 180 miles in forty hours, being at 
the rate of 4^ nules an hour, against a current averaging 
3 miles per hour. 



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CHAPTER II. 

SHIP CANALS. 

Utility ot Ship c&nala — Luignedoo, Forth knd Clyde, and Crinui Caiuli — Ship 
oaiudi divided into three tection* : thow throngh high di«tttct* of coantry ; 
tfarongh low-iying dlBtricta ; and thooe withoat locks, deriving their mter- 
•npply from the lea — Caledonian Can^— Canali of Kotth Holland — Anuter- 
dam Canal^-Soeji CanaL 

The statement at the b^umiiig of the last chapter, Dtuityorsbip 
as to railways having superseded canals, applies to liie 
smaller canals we hare been considering, but is not true of 
the larger class of works still to be noticed. Ship canals 
undisturbed by competing schemes retfun all their usefiil- 
ness, and indeed in the recent construction of the Suez 
and new Amsterdam Canals have acquired an importance 
before unclaimed for works of that daas. Their use- 
fiilness in affording a short and sheltered passage for 
sea-borne vessels, enabling them to escape tedious and 
sometimes dangerous coasting voyages, was early ac- 
knowledged, and can hardly be over-estimated. 

The Ijanguedoc Canal, already mentioned, by a short 
passage of 148 miles saves a sea voyage of upwards of 
2000 miles through the Stiaits of Gibraltar. The Forth 
and Clyde Canal, projected by Smeaton in 1764, and 
opened in 1790, enables sea-borne vessels, not exceeding 
8^ feet draught of water, to pass from oppodte coasts of 
Scotland by 35 miles of inland navigation; and the 



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28 INLAND NAVIGATION. 

Crinan Canal substituteB a short inland route of 9 miles 
for a sea voyage round the Mull of Ejntyre of about 70 
miles. 

To most of the early ship canals ih.a,t have been eze- 
cuted, the principles of construction stated in the pre- 
ceding chapter are generally applicable — ^the depth of 
water and the dimensions of the lochs being increased to 
admit the lai^;er size of craft -which use them, — and there- 
fore I do not propose to describe them further; but it 
would not do to dismiss the subject without referring in 
detail to some of the lai^est of these canals, in order to 
illustrate the diflferent character of work employed to suit 
the varied physLcal aspecta of the countries through 
which they pass, and I think the student of engineering 
win find that the works themselves are so interesting as 
to demand special notice. 
Ship avail I propose to divido ship canals into three sections : — 

diTided into t^T ^ , , . , 

uuMduwa. First, Canals which on their route from sea to sea 

traverse high districts, surmounting ih.e elevation by locks 
supplied by natural lakes or artificial reservoirs, such as 
Languedoc or Caledonian Canals. 

Second, Canals in low-lying districts, which are carried 
on a uniform water-level itx>m end to end, £aid are de- 
fended against the inroad of the sea at high water by 
double-acting lochs, which also retain the canal-water at 
low tide, Budi as the canals of Holland uid other low- 
lying coimtriea. 

Third, Canals of which the Suez is the only example 
yet made, without locks at either end, and communicating 
fi^y with the sea, firom which it derives its water-supply. 



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SHIP CANAIf. 



Caledonian Canal. 



Of each of these iiiree sections I shall give an example. 
And I believe that the Caledonian Canal is as good a 
specimen of tixejirst class as can be selected. 

So early aa 1773, Jamea Watt was employed to survey 
the country between the Beauly at Inverness and Loch 
Eil, at die moutJi of the river Lochy — a distance of about 
60 miles, — ^with the view to the formation of a ship canal 
between the two seas, to save about 400 nules of coasting 
voyage by the north of Scotland, through the stormy 
FentJaud Firth. The district referred to, called the 
*' Great CMedonian Glen," as will be seen from Plate I., 
embraces a chain of fii^eeh-water lakes, which, in con- 
nexion -mih the surrotmding glens, have afforded an 
interesting field for the speculations of the geolc^ist ; and 
no doubt the first conception of a canal through the dis- 
trict owed its origin to the apparent ^cUities for inland 
navigation which the lakes afforded.^ In 1801 Telford - 
was emplc^ed by Government to report, and the ultimate 
result of that report was the construction of the canal, 
which was opened in 1823. 

The summit-leveL of the canal is at La£^;an, which is 
situated between Loch Oich and Loch Lochy, and firom 
this place the drainage flows to the eastern and western 
seas. The district which discharges into the eastern out- 
let comprehends an area of about 700 square miles, chiefly 
of high moimtainous country, intersected by streams and 
lakes, which discharge themselves into Loch Oich, Loch 

* LyiqfTtfford: CkledoniftD CukL 



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30 INLAND NAVIGATION. 

Ness, and Loch Dougbfour, and tbence are conveyed into 
the Moray Firth by tbe river Ness. 

Loch Oich, the summit-level of the canal, has an area 
of about 2 square uules, and the present standard lev^ of 
its surface is understood to be 102 feet above the level of 
mean bigh-water of neap tides in Beauly Firth. It re- 
ceiveB tbe drainage of Loch Quoicb and Loch Garry. Tbe 
waters of Locb Oich are discharged through the river 
Oich into Loch Ness, which is about 24 miles in length, 
and has an area of about 30 square miles. Loch Ness 
receives the waters of the Tarflf, the Foyers, and Glen- 
moriflton, and the drainage of numerous other streams and 
lakes of less note. It discharges its waters through a 
comparatively narrow neck, called Bona Passage, into tbe 
small loch of Doughfour, &om whence they £nd an exit 
to the Beaiily and Moray Firths by the river Ness, aa 
which the town and barbour of Inverness are situated. 
The drainage of tbe western district of tbe country, includ- 
ing Loch Arke^, finds its way into Loch Lochy, wbicb 
is about 10 miles long, and thence, by the river Lochy, 
to the western sea at Locb £il. 

Tbe two locks in Loch Beauly, at tbe northern en- 
trance to the canal, are each 170 feet long, 40 feet wide, 
and have a lift of about 8 feet. At Muirtown, a little 
fiirther on, are four locks, of 180 feet in length and 40 
feet in width, having a rise of 32 feet, raising the canal 
to tbe level of Loch Nees, which it enters at Bona. Tbe 
works westward of Loch Ness consist of an artificial canal, 
with seven locks, communicating with Loch Oich. Be- 
tween Lochs Oich and Lodhy are two locka At the 



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BHIF CANAIB. 31 

south end of Loch Lochy is a r^;ulating lock, and the 
canal ia carried firom thlfl point on the level of Loch 
Lochy to Bannavie, where it descends 64 feet, by eight 
connected locks, forming what is called in the country 
" Neptune's Staircase ;" finally, at Corpach, the canal 
descends, by two locks, to the level of Loch EiL 

Of the whole distance, about 37^ miles may be taken 
- as natural lake navigation, and the remaining 23 as 
artificial. 

The artificial canals were made 120 feet in width at 
top water level, 50 feet at bottom, and 20 feet in depth. 
In the course of inquiries as to the state of the canal in 
1849, under a remit from the Admiralty, I foimd that the 
shaUowa at Loch Oich, and the cutting at the summit- 
level, had not been carried to the full depth, and an addi- 
tional depth had been gained at that place by raising the 
level of Loch Oich ; but stUl I was led to the conclusion 
that the standard depth of the canal cannot be regarded 
as more than 18 feet, giving access to vessels of 160 feet 
in length, 38 feet beam, and 17 feet draught of water.' 

In carrying out this remarkable work Telford had to 
deal with difficulties of no ordinary kind, in rendering 
available rugged Highland lakes, and surmounting the 
summit-level of the glen. The work, which cost about 
one miUion sterling, is a noble monument of his engineer- 
ing alt ill , 

The canals of HoUaud are specimens of the second cuuia of North 
section of works to which I referred, and of these a 

> Report on the C&ledonuHi Canal to the Admiralty, 1849, by Junes Vetch, 
R.E., ud David StoTenMn, C.K 



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93 INLAND NATIQATION. 

•very remarkable one ia the North Holland Canal, de- 
fdgned hy M. Blanken, and completed in 1825, who, 
instead of the Highland glens of Scotland, had to deal 
with the proverbial lovmess of the country, and to protect 
his works from the assaults and encroachments of the 
waves, and when I examined the work they were locking 
vessels down from the sea into the canaL It extends 
from Amsterdam to the Helder, is 50 miles in length, axtd 
is formed of the cross section shown in fig. 5. It enables 
vessels trading from Amsterdam to avoid the islands and 
sandbanks of the dangerous Zuider Zee, the passage 



Fio. S. 

through which, in former times, ojEten occupied as many 
weeks as the transit through the canal now occupies 
hours. 

It was here that Bakker, a burgomaster of Amster- 
dam, in 1688, introduced his "Camel" for floating large 
vessels over the shoals of the Panipus between Amster- 
dam and the Texel Koads, by means of which, according 
to Sir John LeaHe, an Indiaman which drew 15 feet 
water had its draught reduced to 11 feet. The following 
description is ^ven of these camels by Mr, G. B. W. 
Jackson : ^ — " These water camels, of which several were 
kept at Pampus on the Y stream, were used in pairs 
whenever they were required. They were of suffi- 
cient length to suit the Ingest vessel, being each pro- 

> MintiUt <if Proeitdingi <if Inititution qf Civii SngUuen, voL vL p. S2. 



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ng.,z=db,G00g|i 



SHIP CAJHAI£. 33 

vided with a rudder, and with windlasses on the outer 
aide, to which the ropes were attached for securing the 
vessel They probahly had 31 ship's pumps of 6 inches 
diameter for clearing, and about 16 valves for letting in 
the water used to sink them. The complement of men 
for working them was about 50 to each. They weighed 
about 450 tons, drew about 2 feet 3 inches when empty, 
and if weighted with 820 tons about 7 feet 5 inches more. 
They have been broken up, as being no longer required. 

AmSTEBDAM CANAIi. 

But the North Holland Caial, which has long proved 
so useful to t^e commerce of the district, is destined soon 
to be superseded by the New Amsterdam Canal, a work 
of gfeat magnitude, which I propose to describe as an 
illustration of ship canals of the second class, having re- 
ceived, through the kindness of Mr. J. C. Hawkshaw, the 
following interesting details regarding it : — 

The rapid increase in the trade of the ports to the 
southward and eastward of the Holder, effected by the 
construction of railways throughout Eiuxjpe, rendered it 
imperative for the merchants of Amsterdam to provide 
better communication with the North Sea th^i that 
afforded by the North Holland Ship C^ial, already 
noticed, or suffer itfl trade to pass to other ports more 
&vourably situated for over-sea trade. 

In 1865 a company was accordingly formed for the 
purp(«e of constructing a canal from Amsterdam, in 
nearly a direct line, to the North Sea, through Lake Y 
and Wyker Meer, a distance of 16j miles. Mr. Hawk- 



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34 IKI-AND NAVIGATION. 

shaw and Mr. Dirks were appointed the engineers to 
carry out the work, a plan and section of which is given 
in Plate IL 

The harbour in which the canal terminates in the 
North Sea is formed by two piers built of concrete blocks 
founded on a deposit of rough basalt. The piers are each 
5069 feet in length, and enclose an area of about 260 
acres. About 140 acres of this area is to be dredged to a 
depth of 26^ feet, the remainder is to be left at the 
present depth for the accommodation of small craA^ and 
fiahing-boats. 

From its commencement at the harbour the canal 
passes by & deep cutting through a broad belt of sand- 



FlO. 6. 

hiUs which protect the whole of this part of the coast of 
Holland &om the inroads of the se& The croes section of 
the canal at this place is shown, fig. 6. This cutting is 
about 3 miles in length ; the greatest depth from the 
sur&ce to the bottom of the canal is 78 feet; and tiie 
amount of earthwork excavated is 6,213,000 cubic ^ards. 
On emerging from the sand-hills the can^ passes by the 
village of Velsen, in the neighbourhood of which it is 
crossed by the railway from Haarlem to the Helder, and 
there enters the Wyker Meer, a large tract of tide- 
covered land. After traversing the Wyker Mew it passes 
by a cutting of 327,000 cubic yards through the promon- 
tory called Buiten-hindn, which separates that Meer from 



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SHIP CANAIf. 35 

Lake Y, another lai^ tide-covered ai«a. The rest of its 
course lies through Lake Y as &t as Amsterdam. 

There are two sets of locks, one set at either end. 
The North Sea locks are at a distance of about three quar- 
ters of a mile fix)m the North Sea harbour. These locks, 
as shown in fig. 7, consist of three passages. The central 
or main one is 60 feet wide and 390 feet long, and wUl be 



furnished with two pairs of gates at each end, pointing 
in opposite directions, and one pair in the centre. The 
northernmost side passage for barges is 30 feet long and 34 
feet wide, with three pairs of gates; that to the south is 227 
feet in length and 40 feet wide, with five pairs of gates. 

In constructing the canal, which is now fer advanced 
towards completion, the cuttings were first begun. The 
material proceeding from these cuttings was conveyed 
either by means of waggons or baizes, and deposited so 



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36 DTLAin) NATIQATION. 

as to form two banks 443 feet apart, through the lakea 
on each Bide of the main camil, as shown by the hard 
lines on the plan, and also to form the banks of the branch 
canala on either side. The total length of these banks is 
38i^ miles. The nucleus of the bank is formed of sand, 
with a coating of clay, and protected during its progress 
with &8cine8; and when ihe bajika are hi enough ad- 
vanced, the deep channel for the canal is excavated by 
dredging. The cross-aection of the canal and banks 
through these meers or lakes is shown in fig. 8. 

The fonnation of the banks through the Wyker Meer 
and Lake T will enable about 12,000 acres of the area, 



as shown on the plan, whidi is now occupied by these 
lakes, to be redaimed. For the purpose of this reclamar- 
tion, and also to provide for the drainage of the land on 
the matgin of the lakea, including a lai^ portion of what 
was formerly Haarlem Meer, pumps are provided by the 
Company at various points on the main and branch 
canals. The Canal Company are bound to keep the sur- 
fece-water of the canal about 1 foot 7 inches below average 
high-water level In order to insure this level being 
maintained, three large pumps have been erected in con- 
nexion with the locks hereafter to be described, on the 
dam between Amsterdam and the Zuider Zee. They con- 
sist of three Appold pumps, the largest of the kind yet 
made, the &ns belog 8 feet in diameter. Each pump is 
worked by a separate engine of 90 nominal hotae-power. 



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SHIP CASAIA 87 

The maximum lift is 9 feet 9 inchee, at whi*^ ihe three 
pumps are capable of diBchai;ging 1950 tons a minute ; 
witli the ordinaiy workiiig lift of 3J feet they will di»- 
chai^ 2700 tons a minute. Pumps of a similar construo 
tion, with fiins one foot less in diameter, erected some 
years ago under Mr. Hawkshaw's direction, at Lade Bank, 
in IJncolnshire, have been found to work satis&ctorily. 

Lake Y, as will be seen from the plan, extends about 
4^ mUes to the eastward of Amsterdam ; and here it was 
necessary to form a dam with locks for the passage of 
vessels. The dam crosses Lake Y at a point about two 
miles to the eaetward of Amsterdam, where it ia con- 
tracted to 4265 feet in width. 

As it was necessary to construct these locks before 
completing the dam across Lake Y, a circular cofferdam, 
590 feet in diameter, consistuig of two rows of piles, 49 
feet long, was constructed in the tideway, and within 
this dam the locks were built. 

These locks have three main passages, each with five 
pairs of gates, and one smaller passage with three pairs of 
gates, arranged much in the same manner as the North 
Sea locks, shown in page 85, but their dimensions are 
not so large. The central main passage has a length of 
315 feet, and is 60 feet wide. The passages on each side 
of it have each a lengUi of 238 feet, and are 47 feet 
wide. The small passf^ is 30 feet long and 34 feet 
wide. There are also three sluiceways for the pumps, 
each 110 feet long and 13 feet wide, and each provided 
with three pairs of gatea 

The whole of the masonry and brickwork for these 



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38 INLAND NAVIOATION. 

locks and sluicewayB was founded on bearing-piles, up- 
wards of 10,000 in number. 

The bottom where the cofferdam was placed, consisted 
of mud, and some difSculty was experienced in maintain- 
ing it till the work was completed. 

The dam across Lake Y, as shown in section, fig. 9, 
consists of clay and sand, placed on and protected at the 
mdem by hxge masses of wicker-work, which is afterwards 




covered with basalt in the maimer usually adopted in 
Holland. 

AJl the lock gates at both ends of the canal pointing 
seawards are of malleable iron ; the gates pointing in- 
wards towards the canal are of wood. 

The necessity, for drainage purposes, of maint^ning 
the surface-water of the canal at the prescribed low level 
calls for a sufScient barrier being provided against the sea 
at both ends, as the sea-level will not unfrequently, at 
high water, be several feet above the level of the canal 

This necessity, as well as the difference of level and 
periods of high water in the Zuider Zee and the North 
Sea, required a totally different design from the Suez 
Canal, to be ailerwards described. 

The contract sum for the execution of the Amster- 
dam Canal is 27,000,000 of florins, or about ^2,250,000. 



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SHIP CANAIA 39 

It is to be hoped that ships may pass iJirough the canal 
in about two years. 

Suez Canal. 

Of the ^ird section of works there exists as yet only 
a single example, in the Suez Canal, one of the most re- 
markable of the engineering works of modran times ; but 
though it is called a canal, it bears little resemblance 
to the works I have been describLog under that name, 
for it has neither locks, gates, reservoirs, or pimiping- 
engiaes, nor has it, indeed, anythiEig in common with 
canals, except that it affords a short joute for sea-borne 
ships. It is ia &ct, correctly speaking, an artificial arm 
of the sea, or strait connecting the Mediterranean and the 
Bed Sea, &om which it derives its water-supply. 

The idea of forming this connecting link is of very 
ancient origin, and its author is imknown. It is under- 
stood, however, that a water communication between the 
two seas, for small vessels, was formed as early as 600 
years before the Christian era, and existed up to a period 
of about 800 years after that date, and then was allowed 
to &II into disuse. The idea of restoring this ancient 
communication on a scale suited to modem times is under- 
stood to be due to Napoleon L, who, about the close of the 
last century, obtained a report from M. Lepfere, a French 
engineer, which however was followed by no result, and 
it remained for M. de Lesseps, in the present day, to 
realize what were thought the dreams of commercial 
speculators, by carrying out the long-desired passage 
between the two seaa But ihs postponement of the 



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40 INLAND NAVIGATION. 

scheme iinqueetionably fevoured the chancea of its com- 
mercial auccees, for had the canal been completed even a 
few years earlier, comparatively few vessels would have 
been found to take advantage of it. Sailing vesselfl would 
never have navigated the Mediterranean and encountered 
the passage through the canal, and the tedioxis and diffi- 
cult voyage of the Red Sea. They woidd imdoubtedly 
have preferred to round the free seaway of the Cape of 
Good Hope, with all its ocean dangers and excitements, 
to threading their way through such an inland passage, 
involving risks of roc^ and shoals, ' protracted calms 
and contrary winda But the introduction of ocean- 
going screw-steamers was an entirely new feature in 
navigation. Being independent of wind for their pro- 
pulsion, and admirably fitted for navigating narrow pas- 
sages and seas, their rapid and general adoption by all 
the leading shipping firms in the country afforded not 
only a plea, but a necessity for the short communication 
by the Mediterranean and Red Sea. It was indeed 
a great achievement to reduce the distance between 
Western Europe and India from 11,650 to 6515 miles, 
equal, according to Admiral Richards and Colonel Clarke, 
R.E., to a saving of 36 days on the voyage ; and this is 
the great result effected by cutting the Suez Canal be- 
tween the Mediterranean and the Red Sea. 

Mr. Bateman, C.E., who visited the canal as the 
r^resentative of the Royal Society, communicated to 
that body an interesting description of the works, in 
which he gives the following account of the early pro- 
posals and negotiations of M. Ferdinand Lesseps, who 



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BHIF CAI4AI£. 41 

has the credit of having hrought the work to a successful 
issue :' — 

" The project " of M. Ferdinand Lessepe " was to cut 
a great canal on the Wei of the two seas, by the nearest 
and moat practicable route, which lay along the valley or 
depression containing Lake Manzaleh, Lake Ballah, Lake 
Timsah, and the Bitter Lakes. The character of this 
route was well described in 1830 by General (then Cap- 
tfun) Chesney, K.A., who examined and drew up a report 
on the country between the Mediterranean and the E«d 
Sea. At that time a difference of 30 feet between the 
two seas was still assumed, and all proposals for canals 
were laid out on that assumption. Allowance must, of 
course, be made for this eiTor in so £ir as it aSected any 
particular project of canal ; but it would not affect the 
accuracy of any general description of the district to be 
traversed. General Chesney sununed up his report by 
stating, ' As to the executive part there is but one 
opinion : there are no serious difGctdties ;. not a single 
mountain intervenes, scarcely what deserves to be called 
a hillock ; and in a coimtry where labour can be had with- 
out limit, and at a rate infinitely below that of any other 
part of the world, the expense would be a moderate one 
for a single nation, and scarcely worth dividing among the 
great kingdoms of Europe, who would all be benefited by 
the measure.' 

" M. Lesseps was well advised therefore in the route 
he selected, and (assuming the possibility of keeping open 
the c»nal) in the character of the project he proposed. 

> Proceedingt qf Hit Royal Soek/y, 1870, p. 132. 



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INLAND NAVIGATION. 



" From 1849 to 1854 be was occupied in maturing his 
project for a direct canalization of the isthmus. In the 
latter year Mahomet Said Pasha became Viceroy of 
I^ypt, and sent at once for M. Leseepa to consider with 
him the propriety of carrying out the work he had in 
view. The result of this interview was, that on the 30th 
of November in the same year a coiomission was signed 
at Cairo, charging M. Leaseps to constitute and direct a 
company named ' The UniverBal Suez Canal Company.' 
In the following year, 1855, M. Lesseps, acting for the 
Viceroy, invited a number of gentlemen, eminent as 
directors of public works, as engineers, and distinguished 
ID other ways, to form an International Commission for 
ih.6 purpose of considering and reporting on the practica- 
bility of forming a ship canal between the Mediterranean 
and the Bed Sea. This Commission, which included some 
of the ablest civil and military engineers of Europe, was 
honorary, and its members were considered as guests of 
the Viceroy. 

"The Commission met in £^;ypt in December 1855 
and January 1856, and, accompanied by M. Lesseps and 
by Mougel Bey and Linant Bey, engineers, and other 
gentlemen in the service of the Viceroy, they made a 
care&l examination of the harbours in the two seas, and 
of the intervening deeert, and arrived at the conclusion 
that a ship canal was practicable between the Gulf of Pelu- 
sium in the Mediterranean and the Red Sea near Suez. 
They differed, however, as to the mode in which such a 
canal should be constructed. The three English engineer- 
ing members of the Commission were of opinion that a 



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SHIP CANALS. 43 

ship canal having ite sur&ce raised 25 feet above the sear 
level, and communicating "with the Bay of Pelusium at 
one end and the Bed Sea at the other, by means of locks, 
and suppUed with water from the Kile, was the best mode 
of construction. The foreign membeiB, on the contrary, 
held that a canal having its bottom 27 feet hdow sea- 
level, from sea to sea, without any lock, and with har- 
bours at each end, was the best system : the harbours to 
be formed by piers and dredging out to deep water. 

" The Commission met atParisinJime 1856, when the 
vievrs of the English en^eers were, after frill discussion, 
rejected, uid the report to the Viceroy recommended the 
syst^n which has since been carried out. The Commis- 
sion estimated the work to cost £8,000,000. 

" Two years frxim the date of this report were spent 
in conferences and preliminary steps before M. Lesseps 
obtained the necessary iunds for carrying out the works. 
About half the capital was subscribed on the Conti- 
nent, by &r the larger portion being taken id France, 
and {h& other half was found by the Viceroy, Fiirther 
time was necessarily lost in preparation, and it was not 
till near iJie close of 1860 that the work was actually 
commenced. . . . 

" The original concession granted extraordinary privi- 
leges to the Company. It included or contemplated the 
formation of a 'sweet water' canal for the use of the 
workmen engaged, and the Company were to become pro- 
prietors of all the land which could be irrigated by means 
of this canal One of the conditions of the concession 
also was that the Viceroy should procure forced laboiur for 



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44 INLAMD NAVIGATION. 

the execution of the work ; and soon after the commence- 
ment of operations, and for some iime, the number of 
workmen bo engaged amounted to irom 25,000 to 30,000. 
The work thus commenced steadHj proceeded imtil 1862, 
when the late Yiceroy, during his visit to this country at 
the time of the International Exhibition, requested Mr. 
Hawkshaw to visit the canal and report on the con- 
dition of the works and the practicability of its being 
succesaiidly completed and maintained. His Highnees's 
instructions were that Mr. Hawkshaw should make an ex- 
amination of the works quite independently of the French 
company and their engineers, and report, from his own 
personal examination and consideration, the residt at 
which he anived. If his report were &vourahle the work 
would be proceeded with, if unfiivourahle it would at once 
be stopped. 

" Mr. Hawkshaw proceeded to Egypt upon this im- 
portant commission in November of the same year, and in 
February 1863 he wtote a weU-considered report, which 
may be said to have in a great measure contributed to 
the rapid and successful completion of the work. JSi. 
Hawkshaw described the works of the canal which had 
been already executed and those which remained at that 
time unfinished. He examined and discussed the dimen- 
sions of the various parts then in progress, recommending 
various alterations, and, having carefiilly gone into all the 
details of construction, he proceeded to investigate the 
question of maintenance, with reference to which it had 
been urged by opponents — 

" ' 1°. That the canal will become a stagnant ditch. 



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SHIP CAIfAI^. 45 

" ' 2°. That the canal will rait up, or that the moving 
saods of the Desert will fill it up. 

" ' 3°. That the Bitter Lakes through which the canal 
is to pass will be filled up with salt. 

" ' 4°. That the navigation of the Red Sea is dangeroua 
and difficult. 

" ' 5°. That shipping will not approach Port Said, 
because of the difficulties that will he met with, and the 
danger of that port on a lee shore. 

" ' 6°. That it will be difficult, if not impracticable, 
to keep open One Mediterranean entrance to ihe canaL' 

" ECaving analysed each of these objections, and iully 
weighed ^e argumenta on which they were based, he 
came to the following conclusions as to the practicability 
of construction and mmntenance : — 

" ' 1st. Afl regards the engineering construction, there 
are no works on the canal presenting on their &ce any 
unusual difficulty of execution, and there are no con- 
tingencies tliat I can conceive likely to arise iha.t would 
introduce difficulties insurmountable by en^eering skill. 

" ' 2dly. As regards the maintenance of the canal, I 
am of opinion that no obstacles would be met with that 
would prevent Hie work, when completed, being main- 
tained with ease and efficiency, and without the necessity 
of incurring any extraordinary or unusual yearly e^>endi- 
ture.' 

" The whole of Mr. Hawkshaw's report is well worthy 
of perusal, and I must congratulate him on the sound 
conclusions at which he arrived, and on the foresight by 
which he was enabled to point out difficulties and contin- 



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46 INLAND NAVIQATION. 

gencies wHch have since arisen. Could lie at tbat time 
have seen the fiiU realization of the work he would 
Bcareely have altered the report he wrote. 

" Saad Pasha died between the period of Mr. Hawk- 
shaVs examination of the country and the date of his 
report. He was succeeded hy his brother, IsmMl, the 
present Viceroy or Khedive, who, alarmed at the lai^eness 
and uncertainty of the grants to the Canal Company, of 
the proprietorship of land which could be irrigated by the 
sweet-irater canal, and anxious to retire &om the obliga^ 
tion of finding forced labour for the construction of the 
works, refiised to ratify or agree to the concessions 
granted by his brother. The whole question was referred 
to the arbitration of the Emperor of the French, who 
kindly undertook the task, and awarded the enim of 
£3,800,000 to be paid by the Viceroy to the Canal Com- 
pany as indemnification for the Iobs they would sustain 
by the withdrawal of forced or native labour, for the 
retrocession of lai^ grants of land, and for the abandon- 
ment of other privileges attached to ihe original act of 
concession. This money was apphed to the prosecution 
of the works. 

" The withdrawal of native labour involved very im- 
portant changes in the mode of conducting the works, and 
occasioned at the time considerable delay. Mechanical 
appliances for the removal of the material, and European 
skilled labour, had to be substituted; these had to be 
recruited from different parts of Europe, and great diffi- 
culty was experienced in procuring them. The accessory 
canals had to be widened for the conveyance of laiger 



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SHIP CANALS. 47 

dredging-machines, and additional dwellings had to be pro- 
vided for the accommodation of European laboturers. All 
these diflBculties were overcome, and the work proceeded." 
A&eir the works had been nearly completed, the Lords 
of the Admiralty instructed Admiral lUchards, the hydro- 
grapher, and LieutenantrColonel Clarfce, RE., to viat 
Egypt, and report as to the condition of the canaL These 
officers accordingly made a most minute survey of the 
canal and its terminaL harboura, and issued a most intffl^ 
esting report,^ from the information contained in which 
the plan of the canal, Plate HE., has been mainly con- 
structed. On referring to this plan it will be seen that 
the canal extends from Port Said on the Mediterranean 
to Suez on the Bed Sea, and that, as shown hy the 
section, it traverses a comparatively flat country. This 
route has been selected so as to take advantage of certain 
vaUeys or depressions which are called lakes, but were in 
fitct, previous to tie construction of the canal, low-lying 
tracts of country, at some places below the level of the 
Mediterranean and Bed Seas. These valleys were found 
to be coated with a deep deposit of salt, and are described 
as having had all the appefu-ance of being covered with 
snow, bearing evidence of their having been at one period 
overflowed by the sea. As will be seen from the plan, 
Lake Menzaleh is next to the Mediterranean, Lake Timsah 
about half-way across the isthmus, and the Bitter Lakes 
next to the Bed Sea. Lake Timsah, which is about 3 
miles long, and the Bitter I^kes about 23, were qmte dry 

' Report on the Haritinie Ckoal connectiDg the MediterraneMi kt Port 8>Id 
with the Bed Sea tit Snei, Febrnu; 1S70. 



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INLAND NAVIOATION. 



before the cutting of the canal, and the water which has 
converted them into large inland lakes was supplied from 
the Bed Sea and Mediterranean. The water b^;an to flow 
frx>m the Mediterranean in February 1869, and from the 
Bed Sea in July, and by the beginning of October of the 
same year these vast tracts of country, which had for- 
merly been parched and arid vaUeyB, were converted into 
great lakes navigated by vessels of the largest class. It 
will be seen from the section that the sur&ce of the 
ground is generally very low, the chief cuttings benig at 
S^rap^um and £1 Guim-, where the sandy dunes attain 
an elevation of about 50 to 60 feet. The channel through 
the hkee was excavated partly by hand labour and partly 
by dredging, and for a considerable portion the level of 
the valleys was such as to aflTord sufficient depth without 
resorting to excavation. The material excavated appears 
to have been almost entirely alluvial, and easily removed ; 
the only rock was met with at El Guier, where soft 
gypsum occurred, removable to a considerable extent by 
dredging, so that the canal works may be regarded as 
having presented no physical difficulty. 

The following details as to the dimensions of the work 
are chiefly suppHed from the Admiralty report, already 
referred to. 

The whole length of the navigation is 88 geographical 
miles ; of this distance 66 nules were actual canal, formed 
by cuttings, 1 4 miles were made by dredging through the 
lakes, and 8 miles required no works, the natural depth 
being equal to that of the canal. Throughout its whole 
length the canal was intended to have a navigable depth of 



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SHIP CANAU. 49 

26 feet for a width of 72 feet at the bottom, and to have a 
width at the top varying according to the character of the 
cnttinga. At these places where the cuttings are deep, the 
slopes were intended to be 2 to 1, with a surfece width at 
the iroter-line of about 197 feet, as shown in fig. 10, which 
is a cross section at El \ / 

GuisT ; in the less ele- 
vated portions of the 
land, where the stuff is ^"^ *"• 

softer, the slopes were to be increased, giving a surfitce 
width of 325 feet. Of course it will be understood that 
in the lakes the canal con«st6 of a navigable channel of 
sufficient depth and breadth to admit the traffic, the sur- 
&ce of the water extending on eitJier side to the edge of 
the lake. Fig. 11 shows a cross section at Lake Manzaleh. 
At the date of the Admir^ty inspection, these dimen- 
sions had not in all 



^^r^ 



respects been fully at- n ^^^^ p ^ -^ 

tained, tiie depth at ^^"'*~* 

some places varying 

from 20 to 22 feet, but the Admiralty officers reported 
that the deepening of the shallows is in progress, and that 
they are likely soon to be removed. The curves, they also 
report, are sharp, requiring great care and attention in 
piloting vessels. The deep channel through the lakes is 
marked by iron beacons on either side, 250 feet apart, and 
the Admiralty reporters state that "in practice it is 
foimd more difficult to keep in the centre while passing 
tJirough these beacons, than it ia when between the em- 
bankmenta" At every five or six miles there is a passing- 



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50 INLAND NAVIGATION. 

place, to enable large vesaels to moor for the night, or to 
bnng-up, in order to allow others to pass. At each of 
t^em a telegraph Htatiou is to be established, with an 
oflEcer who is to r^;u]ate ihe movements of passing vessels 
according to directions which will be communicated from 
Port Said, Ismailia or Suez. 

Perhaps the most interesting question to the engineer 
is that which relates to the action of the tide between the 
two seas, and in so ^ir as observations have been made, 
they are given in the following quotation from the Ad- 
miralty report : — " The tidal observations which we were 
able to make were necessarily somewhat imperfect from 
want of time, but they were made at that period of the 
moon's age when their effect- would be greatest ; the 
results show ths-t in the southern portion of the canal, 
between Suez and Great Bitter Lake, the tidal influence 
from the Red Sea is felt, there being a regular flow and 
ebb ; the flood running in for about seven hours, and the 
ebb running out for five hours; at the Suez entrance, 
tiie rise at springs, unless effected by strong winds, is 
between 5 and 6 feet ; about half way frx)m Suez to the 
SmaU Bitter Lake, a distance of 6 miles, it is under 2 
feet ; at the sout^ end of the Small Bitter Lake, a few 
inches only ; while at the south end of the Great Ijake 
there is scarcely any perceptible tidal influence. We 
were informed by the authorities at Ismailia, that since 
the Great Lake has been filled, the level of Lake Timsah, 
which was filled fitan the Mediterranean in April 1867, 
has risen 12 centimetres, or about 4 inches ; and that its 
waters are continually running at a alow rate into the 



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SHIP CANAIA 51 

HediterraaeaD ; certainly this statement agreed with what 
we oiirselveB remarked, for we always found a current 
running northward &om Lake Timsah at the rate of firom 
half a mile to a mile an hour. Limited, however, as these 
tidal obeervationB were, they were taken with great care, 
and appear sufficient to show that, except at the Suez 
end, t^e tides will not materially affect the passage of 
vessels ; at that end, therefore, laige vessels must regulate 
their time of passing; indeed, the greatest difficulty which 
will he experienced will be not from the tides but from 
the prevailing nortii-east wind in the canal, which will 
make close steerage difficult in going from north to 
south." 

It would be highly interesting and valuable to have 
observations made simultaneously at various points, to 
ascertain the action of the tide. All that is at present 
known is contained in the Admiralty report, and ap- 
pears to be, as already stated, that the tidal column of 
5 feet range in the Bed Sea is reduced to 2 feet at the 
distance of 6 miles, and is practically annihilated by the 
wide expanse of the Bitter Lakes. 

In executing this strange work of the desert, and con- 
verting dry sands into navigable lakes, it is stated that 
there have been about eighty milhons of cubic yards of 
material excavated, and at one time nearly 30,000 
labourers were employed on the works. For their use 
a supply of fresh water was conveyed from the Nile at 
Cairo, and distributed along the whole length of canaL 
This work was one of no small magnitude. The fresh- 
water condmt is an open channel from Cairo to Ismailia, 



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52 INLAND NAVIGATION. 

and thence to Suez the water ia conveyed in pipes. The 
surplus fresh water is applied to the irrigation of the 
adjacent country. The cost of the whole undertaking, 
including the harbours, is stated to have been £16,000,000, 
and it is expected that probably £300,000 may still be 
required for its fiiU completion. 

The terminal harbouia are important adjuncts of this 
great work. That on thd Mediterranean is Port S^d, 
which is shown on Plate III. It is &rmed by two break- 
waters constructed of concrete blocks ; the western one 
6940 feet in length, and the eastern 6020 feet, ^iclosing 
an area of about 450 acres, with an average depth of only 
13 or 14 feet, excepting in die channel leading to the 
canal, where the depth is 25 to 28 feet. 

The entrance to the canal at Suez is also protected by 
a breakwater, and, in connexion with the harbour at this 
place, there are two large basins and a dry dock. 

As regards the capabilities of the canal for navigation, 
the Admiralty reporters state that it is a convenient 
highway for all steam-ships or vessels towed, ranging 
between 250 and 300 feet in length, with 35 feet beam, 
and a draught of 20 feet ; for vessels of larger class the 
canal is not so well adapted, and special arrangementa 
would require to be made and enforced for the transit of 
large vessels. Even veasda of 400 feet long, with 50 feet 
beam and 22 feet draught, could be taken through, hy 
adopting special precautions. A delay of three days is 
calculated on for the passage across from Port Said to 
Suez. 

Many fears have been expressed as to the feasibihty 



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BHIF CANALS. 53 

of mftintAining this artificial passage at a remxinerative 
expense to ita constnictors, on account of its being silted 
up by ^e drift-sand of the desert, as well as that 
brought in by the tidal currents — the wastiitg of the 
soft bants by the passage of vessels — and the difficulty 
of obviating the silting up of Port Said by sand carried 
through the open work of which the breakwater is 
formed, and depodted in the area of the harbour. This 
treatise, however, is not the place to discuss the probable 
success or iailiu^ of en^eering works ; all I profess to 
do is to explain the principle on which these works are 
designed, and give examples of such as have been suo- 
crasiully completed ; and certainly, whatever may be the 
future &te of the Suez Canal, either as an engineering 
work or as a speculation, all praise must be accorded to 
M. Lesseps and his stafi^ for having, in the &ce of great 
difficulty, successfully executed one of the most remarkable 
feats of modem engineering. 



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CHAPTER III. 

THE COHPABTMENTS OF RIVERS DEFINED. 

CompartmentB of riven — Their phjsickl ohanoterUtic* deioribed— EiMopls of 
Dornoch Firth — BooDduies of compartmenta not mlwiifB distinct — Different 
compartment* nqnin dittinct engineering worka for tbeii improvement. 

Difbranee Froh what hsB been said, it will be seen that a 

aodKiMr canal ia a work by which water is diverted from its 
navigatioB. natural couTse, and made to occupy a channel prepared 
for its reception, extending through the country for the 
transport of boats and vessels. Canal navigation is 
thus entirely arti/loial in its character. In this respect 
it differs from river navigation, which may be described 
as the art of using, for the purposes of inland communi- 
cation, rivers flowing in t^eir natural courses, and of 
applying means to render them subservient to the pur- 
poses of navigation in cases where the depth is limited, 
or where rapid currents exist. Our consideration of rivers 
must therefore necessarily comprehend a general sketch 
of their physical characteristics, and ^e laws of their 
motion, as a necessary introduction to the practical part 
of ^e subject, which deals with the engineering works 
required for their improvement. 
The compart- _^ introductory, therefore, to the remarks which are 

menti dewribed " 

in riyon. 



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THE C0HPAHTH£N1S OF KIVERS DEFINED. 55 

me in 1845, in a oommnnication to the Boyal Society of 
Edinbuigh,' that in all liTers affected by tidal influence, 
two phjmcal boundarieB, more or lesB apparent, according 
to circumatanceB to be afterwards noticed, are in-variably 
foimd to exist, caused bj the influx of the tidal wave 
through firths or bays, and the modification it receives 
in its passage up the gradually ri«ng inclination or 
slope of a river's bed. These boimdariee agun produce 
three compartmenta.' The seaward, or lowest of these, I 
termed the "aea^>roper;" the next, or intermediate one, 
into which the sea ascends, and from which it again with- 
draws itself, I termed the "tidal compartment of the 
river;" and the highest, or that which is above the in- 
fluence of the sea, tJbe "river proper." Their relative 
extent in different situations is influenced not only by 
the circumstances under which the great tidal wave of 
the ocean enters the riv^, but by the size of its stream, 
the configuration and the slope of ita bed, and, in 
short, by every natural or artificial obstruction which is 
presented to the free, flow of ^e tidal currents along its 
channd. 

These three compartments possess vny different phy- nnir phritoi 
Bical charactenBtic& The presence of umpypoArea ttaal 
phenomena in the lowest, the modified flow of the tide, 
produced by the inclination of tJie river's bed in tiie in- 
termediate, and the absence of all tidal it^luence in the 
highest compartment, may be shortly stated as the phe- 
nomena by which these spaces are to be recognised. The 

■ ProetedingM o/the Bogal Sodttf qf Bdmburgh, toI. iL p. 2S. 

' Lord Cockbnro, in •ddrsMing ■ jury in 1837. ^ipMi* to Iut« aUted 



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56 INLAND NAVIGATION. 

tides in the " sea proper " compartment of an estuary, 
for example (although the place of observation be several 
miles embayed from what in etrictneas could be called 
the " eea" or " ocean"), will be found to resemble those 
of the adjoining sea with which it communicates, — First, 
in the identity of the levels of low water ; second, in the 
shortness of the time which elapses between the cessation 
of ebbing and the commencement of flowing, or, in other 
words, the absence of any protracted period of low water, 
during which the surface appears to remain stationary at 
the same level ; third, in the e^^mmetrical form traced by 
the passage of the tidal wave ; tuid fourth, in the rar^ of 
, tide, BO&xaa that ia not influenced by the formation of the 
shores in narrow seas or channels. In ascending into the 
intermediate compartment, however, the level of the low 
water is no longer the same ; the range of tide, excepting 
in peculiar cases, becomes less, and is gradually decreased 
as the bed of the river rises, and at length a point is 
reached where its influence is not perceptible. In this 
intermediate section the phenomena of ebbing sjid flowing 
are still found to take place, but the times of ebb and 
flow do not remain constant, that of ebb gradually gain- 
ing the ascendency, and in some cases never entirely 
ceasing, though the level of the river be rising. The 
duration of low water is also gradually protracted as we 
proceed upwards, until the influence of tide is imknown. 
This forms ihe boundary-line of the upper compartment, 
the characteristic of which is the total absence of ebbing 
and flowing ; the river at all times pursuing its down- 
ward course in an uninterrupted stream, and at an un- 



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THE C0MPABTMENT8 OF RIVERS DEFINED. 57 

varying level, except in so £ir as may result from the 
cliaiigee due to land floods. 

In the investigation of these different chatacteristics, 
the variable nature of the elements to be dealt with must 
be kept in view. The river, for example, is liable to be 
affected by floods, and the state of the tides by winds 
and other causes ; and therefore a great degree of preci- 
sion in defining these spaces cannot in all cases be ex- 
pected. But the termination of the low-water level at 
the Beparation of the seaward and intermediate spaces, 
as laid down by marine surveyors, simply from observa- 
tion of the tidal phenomena, baa in several dtuations 
been found to agree exactly with the position of that 
boundary as determined by engineers by means of acciu-- 
ate levelling, combined with careful tidal observations. 

An example in actual practice will best illustrate what 
IB meant, and for this purpose I shall refer to the investi- 
gation of the tidal phenomena of the Firth of Dornoch ndu pheuo- 
and Kyles of Sutherland in Cromartyshire, made by me oomocb FMh. 
in 1842. By referring to the small chart of the Dornoch 
Firth in Plate IV. the reader will be better able to fol- 
low the illustrations to be given. The harbour of Port- 
mahomac, marked A on the chart, about 3 miles from 
Tarbetness Lighthouse, was selected as the place at which 
to observe the ocean or sea wave. The second station at 
which it was found convenient to institute observations 
■vras within the Firth at M^kleferry, marked B, about 
3 miles above the town of Tain, and 11 miles distant from 
Portmahomac. The third station was at Bonar Quarry, 
marked C, situated on the north shore of the Firth, and 



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58 INLAND NAVIGATION. 

8 miles inland from Meikleferry ; and the foiirth station 
waB at Bonar Bridge, marked D, one mile from the Bonar 
Quarry. Beyond Bonar Bridge the observations were 
also extended as &r as the junction of the rivers OykeU 
and Casaley, marked E, a distance of 12^ miles ; so that 
the whole distance embraced in the investigation was 33^ 
miles. Graduated tide-gauges were fixed at Portmar 
honuKs, Meikleferry, Bonar Quarry, and Bonar Bridge ; 
and by means of two distinct sets of levelling observa- 
tions, the heights of the zeros of these gauges, in relation 
to each o4^er, were accurately determined, so that all the 
tidal observations made at them could be reduced to the 
LoT-vauriias samo dotum Una The result of the tide observations 
fromPoitnu- was, that the low water of each tide i$, pmctuxdly speah- 
Bonar Qiurr;. i^g, oti the some Uvd cU Portmohomoc, Mmkleferry, and 
Bonar Quarry. I use the word practically, because the 
level of the sea is more or less affected by every breeze 
of wind, which necessarily must pen up and elevate some 
portions of its sur&ce, and cause corresponding depres- 
sion at other places, so that an unvarying low-water level 
will not be found to exist throughout a series of tides on 
any part even of the ocean itself, however limited the 
number of low waters embraced may be. Accordingly, 
deviations of a few inches £ix)m the true level occasion- 
ally occurred in the observations made at the Dornoch 
Firth ; but these were not of greater extent than could 
reasonably be traced to the effect of wind, and were 
found to vary, not only in their amount, but also in their 
value, being at the same gauges sometimes plus and 
sometimes minus quantities, causing corresponding varia- 



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THE COMPARTMENTS OF RIVERB DEFINED. 59 

tions in ^e results deduced firom the different seiies of 
tidal obeervations that were mada Some of these showed 
the low water within a fraction of an inch of being level ; 
while others gave a notable devotion at some of the sta- 
tions ; and others, again, gave a depression below the 
level line at tfie very Btations where previoudy there had 
been a rise. 

To illustrate this more fully, I shall give a few ex- 
amples : ThTiB, on the 23d of June (on which day the 
weather happened to be very calm), the level of low water 
at Meikleferry was three-quarters of an inch above that at 
Portmahomac ; and on the next day, the wind blowing 
fresh from the B.E., the level of low water at Meikleferry 
was 3f inches above that at Portmahomac. Again, a suc- 
ceeding observation gave the level of .Meikleferry three- 
quarters of an inch below Portmahomac. In the same 
way, and in similar small degrees, the level between the 
low water at Bonar Quarry tide^;auge and at Portma- 
homac was found to vary. The average of all tiie obser- 
vations made gave the level of low water at Meikleferry 
2*2 inches above that at Porteoahomac, and the level of 
low water at Bonar Quarry I'l inch heloto the low water 
at Porbnahomac. Whether these average differences of 
level be traceable to the effects of prevailing winds, which 
may be supposed to have exerted a greater influence on 
the water at the more exposed stations, or to any in- 
accuracy in the levels, must evidently, from the examples 
given of the extent and nature of the daily deviations, be 
a point which we cannot determine ; but the result of 
a lengthened train of observations, notwithstanding the 



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60 INLAND NAVIGATION. 

average difference above atated, may feirly be held to be, 
that the low water of each tide is ^racticaUy on the same 
level at Portmahomac, Meikleferry, and Bonar Quany ; 
and therefore that the loio-water tidal phenomena, 
throughout the whole extent of the firth, correspond with 
those of the sea. 
Titer tiwa But whon the results of the observations at Bonar 
IT Bridge. Bridge come to be compared with those made at the 
station immediately seaward of it, a very marked difTer- 
ence presents itself ; for, while the low-water line is found 
to be practically level from Portmahomac to Bonar 
Quarry, a distance of 20 miles, throughout a narrow firth, 
varying fix)m 1^ mile to 550 feet in breadth at low water, 
we find that between the Quarry and Bonar Bridge, a 
distance of only 1 mile, there is a rise in the low-water 
line of spring-tides of no less than 6 feet 6 inches. It 
was therefore concluded that, in the Dornoch Firth, the 
point at which the low-water level of spring-tides met the 
descending current of fr-esh water lay somewhere between 
the Quarry and Bonar Bridge. A different series of 
observations was made to ascertain the exact point at 
which this junction takes place, and the result of these 
observations was, that at low water of an ordinary spring- 
tide, rising 14 feet at Meikleferry, the low-water level of 
the sea meets or intersects the descending firesh-water 
stream from the Kyle of Sutherland, at a point 1700 
yards below Bonar Bridge, or nearly opposite Kincardine 
Church, and within 60 yards 6f the Quarry station. Be- 
tween this point and the Bridge, a distance of 1700 yards, 
there is a rise of 6 feet 6 inches, giving an average slope 



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THE COMPAKTMENT8 OF BTVEBS DETINED. 61 

on ihe sur&ce of the river of 1 in 784, or 6'7 feet per 
mile. 

In addition to thia uniformity in iixe level of low 
water, it was further found that the tidal phenomena of 
the firth corresponded to that of the adjoining sea, in the 
outline traced bj the passage of the tidal wave, as de- 
duced from observations made at the different stations on 
the rise and fell of the tide-level between the periods of 
low and high water. During the period between each 
low water or high water the level of the eurfece was ever 
varying, there being no lengthened cessation of ebbing 
and flowing, the tide-wave being faHj developed at the 
whole of the stations up to Bonar Quany. The range of 
tide was indeed increased in the inner part of the firth to 
the extent of 9 inches at MeUdefeny, and 12 inches at 
Bonar Quany ; that is, when the range of tide was 12 
feet 8 inches at Portmahomac, it was 13 feet 5 inches at 
Meiklefeny, and 13 feet 8 inches at Bonar Quarry. 

But if we inquire into the tides at Bonar Bridge, we r 
find that they do not correspond with those of the adjoin- 
ing sea or of Uie firth ; tor, taking the tide to which we 
have already alluded, which rose 13 feet 8 inches at 
Bonar Quarry, it was found on the same day to rise only 
6 feet 10 inches at Bonar Bridge ; the difierence between 
the two results being occasioned by the rise on the low- 
water line of the channel between these two places. The 
tide on the particular day alluded to rose 6 feet 10 inches 
at Bonar Quarry before it affected the gauge at Bonar 
Bridge, when it b^an to rise at that place also, and after- 
wards continued to flow nearly uniformly at both places. 



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INLAND NAVTQATION. 



Fig. 12 ia a diagram illuflfcrative of the form of the tide- 
-wave at Meiklefeny and Bonar Bridge : the hard line 




Fio. 12. 

represents the curve formed by the passage of the tidal 
wave at Meiklefeny, and the dotted line shows that at 
Bonar Bridge. In both cases the yertical space represents 
the rise of tide, and the horizontal space the elapsed time. 
From this diagram it will be seen, that while the tide at 
Meiklefeny is symmetrical, and presents a constantly 
rising or felling outline, the tide at Bonar Bridge repre- 
aents a long period, extending on some occasions by 
actual observation to fieveral hours at low water, nearly 
unaffected by tidal influence, during which period the' 
water stood almost at the same leveL The tidal water 
admitted into the upper part of the estuary above Bonar 
Bridge took a considerable time to drain off through the 
narrow water-way at that place, and hence the water did 
not attain a permanent low-water level, even long after 
the tide had ceased to operate in affecting its sur&ce. 
The observations made to ascertain how &r the tidal in- 
fluence extended up the Kylea of Sutherland were con- 
ducted with the same care, and proved that the highest 
point influenced by the tide was at the junction of the 
rivers Oykell and Cassley, 12^ miles above Bonar Bridge. 
In stating, however, that the low waters at Portmahomac, 



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THE COHPABTHENTS OF EIVEBS DEFINED. C3 

Meiklefeny, and Bonar Bridge are on ihe same level, the 
reader must not inier that the Bor&ce of the water 
throughout the firth presents at any period a level plane. 
Although the low waters are identical as regards level, 
the times of low water are not the same. On the con- 
trary, the time of low water at Meiklefeny was sometimea 
found to he 50 minutes later than at Fortmahomac, 
and that at Bonar Quarry 50 minutes later than at 
Meiklefeny, so that when the water had attained its 
lowest level at Bonar Quarry it had been riaing for 1 hour 
and 40 minutes at Portmahomac ; there is, therefore, at 
no period a level plane extending throughout the firth, 
but what may be termed a conBtantly undulating Bui&ce. 
This will be better understood when we come to treat of 
tide obsOTvations, and to diow their results as obtained 
on diflWent rivers. 

A further test of the " sea proper " wiU, it is beUeved, Mem »e*-iOT«i. 
be feund in the existence, at any place of observation 
within that compartment, of a central point in the vertical 
range of tide firom which the high and low water levels of 
every tide are very nearly equidistant. The existence 
of such a point was, it is beheved, first determined by 
Mr. James Jardine, at the Tay, in 1810,' and has been 
observed in the firths of Forth and Dornoch, at the 
Skerryvore Bocks on the west of Scotland, at the Isle of 
Man, and in the Mersey. These different series of obser- 
vations, made at points so &r distant £*om each other, 
seem to prove the imiversality of the phenomenon, at 
least on the shores of this country. But in ascending 
' Bepoft by Junea Jaidine, C.E. 



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64 INLAND NAVIGATION. 

into the tidal compartment, the rise on the low-water 
level, which has ah^ady been described, destroys at once 
the symmetry of the tide-wave, as shown in fig. 12, and 
the existence of any such central point equidistant from 
the high and low water level of each tida 

The case I have adduced serves to illustrate the defi- 
nition I have given of the compartments of rivers. From 
Portmahomae to Kincardine, near Bonar Quarry, we have 
EiU the evidences of what I have termed the " sea proper ;" 
the line traced through the low-water mark at difterent 
parts of the firth is practically level ; the curve formed by 
the rise and fidl of the tide is symmetrical ; there is no 
lengthened cessation of ebbing and flowing at the period 
of low water, and the range of tide is unmodified save by 
the additional rise due to the narrow firth through which 
the tide-wave passes. From Kincardine to the junction 
of the Oykell and Cassley we have proofe no less evident 
of the modified flow of the tide peculiar to the " tidal com- 
partment." Even at Bonar Bridge, 1 mile above the 
Quarry, the low- water level is 6 feet 6 inches higher than 
at the station below. At low water the tide remains 
within a few inches of the same level for several hours, 
and its maximum range is reduced to about one half of 
what it is fiirther seaward, while at the junction of the 
Oykell and Cassley it disappears altogether. Above this 
point no tide is known to affect the flow of the stream, 
which, being free from all tidal iofiuence, may be termed 
the " river proper." 
^~V^ I must here warn the reader not to suppose that the 

eqiuiiy dirtinct boundaries we have traced as ezistintr in the Dornoch 

in all casu. o 



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THE COHPABTHENTS OF BITEBS DEFINED. 65 

Firth, and other pkces which I have investigated, may be 
detennined with the same precision under all circum- 
stancefl and ia every caae. The observations to which I 
have alluded are supposed to be made at periods when 
the river is &ee from floods and the sea unaffected by 
heavy gales ; moreover, the configuration of the bottom 
and shores of a river and estuary may, in certain cases, 
render Hie accurate determination of the boundaries very 
difficult. All that I state ia, that these compartments 
do in some measure, more or less defined, exist in all 
rivers debouching through firths and estuaries on a coast 
where the sea has a notable range of tide. These are 
the general features of the rivers in this country, but in 
places where the range of tide is barely perceptible, such 
as the Mediterranean, or where the river joins the 
ocean by a short and steep descent, as will be after- 
wards noticed, the boundaries I have defined cannot be 
easily traced. 

The three compartments which have been defined as DiffaTent com- 
existing in rivers and estuaries naturally lead to a con- nqmn diitinct 



veni^it division of our subject in treating of River Engi- ,oA» for tt«ir 
neering ; for it so happrais that the physical characteristics 
described as peculiar to each of the compartments are not 
less distinct than the engineering works required for their 
improvement. Thus, for example, on the " river proper " 
section the works may be said, in general terms, to consist 
chiefly of weirs built across the stream, by which the 
water is dammed up and forms stretches of canal in the 
river's bed, with cuts and locks connecting the different 
reaches. The "tidal compartment" embraces a more 



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66 INLAin) NAVIGATION. 

varied range of ■work, including tiie straiglitemng, -widen- 
ing, or deepening of the courses and beds of rivers — the 
formation of new cuts, the erection of walls for the 
guidance of tidal currents, and, ia some cases, the 
shutting up of Bubsidiaiy channels, — while the "sea- 
ward compartment" embraces such works as have for 
their object the improvement or removal of bars and 
shoals. AH of these works wiU be treated in succeeding 



It is necessary, however, to explain that no engineer 
is able to consider and advise as to the improvement of 
any portion of a river or estuary unless he is furms h ed 
■with such data for his guidance as can be acquired only 
by accurate surveys and observation of its physical char- 
acteristics. Moreover, as it is impossible for the engineer, 
without possessing these data, to design improvements, 
so, I apprehend, it will greatly assist the student of 
Engineering if, before describing river-works, and showing 
their application in practice, I should give a brief sketch 
of some of the most important hydrometric investigations 
connected with river engiDeering. These include, wnong 
other things, accurate tidal observations and soundings, — 
the determination of a rivOT's slope, velocity, and dis- 
charge,— the natiu« of its bed and banks, and other 
cognate inquiries, and I shall confine my notice to such of 
those topics as are hkely to be most use&l in illustrating 
or rendering more intelligible the subjects treated in the 
succeeding chapters, and must refer the reader for iull 
particulars as to the character and ertent of such in- 
formation, and the means of accurately obtaining it, to 



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THE COUPARTMBNTS OF RIVEEtS DEFINED. 67 

works on River and Marine Surveying. ' Neither do I 
propose to include in the pres^it treatise any account 
of the interesting and gradual progress made hy philo- 
sophers and engineers of the early Italian and French 
schools in theoretical and experimental investigations of 
the laws which regulate the flow of water in natural and 
arti£cml channels, and form the groundwork of all our 
practice in hydraulic engineering. These lengthened and 
laborioxis experimental researches will be found most fully 
discussed — historically, theoretically, and practically — ^in 
the article by Dr. Robison, on the " Theory of Rivers," in 
the Sncyclopadia Britannica, and also in the reports made 
by Mr. George Ronnie to the British Association " On 
the State of our Knowledge of Hydraulics as a branch of 
En^eering,"* to which I refer the reader. 

> AppBcation of Marine Surveying and Bydrfrmetry to the Praetiee qf Civil 
En^fiMerimg. By D>vid SteTengon, Civil EDgiaeer. Edinburgh, 1842, A. AC. 
BiMk. 

* Stporit qfBritiah Aitodalion/or Advancement qfSaenet, 1S33 and 1834. 



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CHAPTER IV. 

HYDBOUETIUC OBSERVATIONS. 

TidM of liren— VarutioDi in the tadal liaea — Prafenor Bobison'* reinarka on the 
uiomaliM of rirer tidea — Natnre of the inqoiry into river tida — Tide-gMigM 
— SelectioD of itttioni for tide obaerrfttioni — Agenti which prodaco distnrb- 
anoe in the paiallelimn of the tidal line* — Manner in which theae Tariation* 
affect the aooDdingi — Datum line for ioondingt — Uw of tide-ganget in rednoing 
■onndings to the datum — Formola for their redaction — Formula only true on 
the aappoaition of the lines being parallel to high water_-Be«uIta affeoted hy 
eironeon* luppodtioa — Moat eSectoal meaai of aToiding inaaoiiiacy ; bnt 
tbi* not alwaya practicable—Oeoeral rolei for taking loundinga— High and 
low water toundinga — Formnin for aacertaining the ri«e of tide and height ef 
tandbanka — Croea tectiona — Mr. Henrj Mitohell'a nle for determining eleva- 
tioni along a tidal river without levelling ; not applicaUe to riven in thia 
oonntiy. 

The hydrometric obeervations to be first noticed are 
those of the tides, and it is essential that they be scrupu- 
lously correct, as they determine the accuracy of all sound- 
ings of the depth of water, and of all sections of the bed 
of the river, which are generally constructed from the 
data afforded by the sounding-line. The information 
afforded hy the tidal and other hydromefcric observations 
is also iudispensable, as will afterwards be seen, in en- 
abling the engineer to form an opinion on many important 
questions that are being constantly brought before him, 
and I therefore offer no apology for discussing this part 
of the subject at some length. 

The tides of rivers are influenced partly l^ the circum- 
stances under which the great tidal waves of the ocean 



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HYPBOMSmUC OBSERVATIONS. 69 

mter iii&i months or estnariee, and partly bj the size of 
the streams and the configuration of the beds and banks 
of the rivers themselves, all of which have a ^lore in 
modifying the free flow of the tidal currents along their 
channels. As no rivers are to be met with whose com- 
mimication with &6 sea, and the course and strength of 
whose streams are in all respects similar, corresponding 
dissimilarities naturally oocur in the drcumstaiices attend- 
iDg the rise and &11 of river tides. If it were correct to 
assume that the high-water mark of each tide, at any 
given nmuber of points in a river's course, stood invari- 
ably on the same level, — ^that the times of high water at 
these points were the same, — and that the prt^^resrave 
rise and &U of the 'tides were uniform and equal at every 
point, — or, in other words, that the sectional lines formed 
by the sur&ce of the water at all periods of flood and ebb, 
which I term the " tidal lines of the river," were parallel 
to the line of high water, — ^the work of the engineer in. 
acquiring data would be greatly simplified. But if he 
were to make such an assumption the groundwork on 
which to found his opinions and fiiame his deugns, his 
conclusions would almost invariably be formed on erro- 
neous data, as his soundings and sections would in most 
cases be inaccurate. 

The following remarks by Professor Eobison,* lUustrar- Anonudiei of 

.... . . riwtld«. 

tive of some of the anomalies in river tides, are interesting 
in connexion with this subject. 

Begarding the rise or inclination which in certain 
circunastances occuis in the high-water line, from the 

' Bobiion'i Meehanieal Pkiloaophy (Bremter'* Edition), vol. iiL p. S63. 



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70 INLAND NAVIGATION. 

entoance of a river upwards. Dr. Eobison says : — " When 
a wave of a certain magnitude enters a channd, it has a 
certain quantity of motion, measured by the quantity of 
water and its vdocity. If the channel, keeping the same 
depth, contract its width, the water, keeping for a while 
its momentum, must increase its velocity or its depth, or 
both, and thus it may happen that, although the greatest 
devation produced by the joint action of the sun and 
moon in the open sea does not exceed 8 or 9 feet, the tide 
in some singular situations may mount considerably 
higher. It seems to be owing to this that the high water 
of the Atlantic Ocean, which at St. Helena doee not ex- 
ceed 4 or 5 feet, setting in obliquely on the coast of 
North America, ranges along that coast in a channel 
gradually narrowing till it is stopped in the Bay of 
Fundy as a hook, and th^re it heaps up to an astonishing 
degree." Again, as to the variation in the times of high 
water at different points, and the nan-parallelism of the 
tidal lines, he says : — " Suppose a great navigable river, 
running nearly in a meridional direction, and felUng into 
the sea in a southern coast. The high water of the ocean 
reaches the mouth of the river (we may suppose) when 
the sun and moon are together in the meridian. It is 
therefore a spring-tide high water at the mouth of the 
river at noon. This checks the stream at the mouth of 
the river, and causes it to deepen. This again checks the 
current &rther up the river, and it deepens there also, 
because there is always the same quantity of land water 
pouring into it. The stream is not perhaps stopped, but 
only retarded But this cannot happen without its grow- 



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HYDROMETRIO OBSERVATIONS. 71 

ing deeper. This is propagated ferther and ferther up 
tlie stream, and it ia perceived at a great distance up the 
rivOT. But this requires a OTnsiderable time. We may 
suppose it just a lunar day before it arrives at a certain 
wharf up the river. The moon at ihe end of the day ia 
again on the meridian, as it was when it was spring-tide 
at ihe mouth of the river, the day before. But in this 
interval the/re has been another high water at the mouth 
of the river, at the preceding midnight, and there has just 
been a third high water about 15 minutes before the 
moon came to the meridian, and 35 minutes after the sun 
has passed it. There must have been two low waters in 
the interval at the mouth of the river. Now, in the same 
way that the tide of yesterday noon is propagated up the 
stream, the tide of midnight has also proceeded upwards, 
and thus there are three co-existent high waters in the 
river. One of them is a spring-tide, and it is fer up at 
ihe wharf above mentioned. The second, or the midnight 
tide, must be haJf-way up the river, and the third is at 
the mouth of the river. And there must be two low 
waters intervening. The low water, that is, a state of 
the river below its natural level, is produced by the pass- 
ing low water of the ocean, in the same way that the 
high water was. For when the ocean &ll8 below its 
natural levd, at the mouth of the river, it occasions a 
'greater dechvity of the issuing stream of the river. This 
must augment its velocity ; this abstracts more water 
from the stream above ; and that part also sinks below 
its natural level, and gives a greater declivity to the 
waters behind it. And thus the stream is accelerated. 



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72 INLAND NAVIOATION. 

and the depth is lessened in Bucxsrasion, in the same way 
as the oppomte effects were produced. We have a low 
water at different wh^& in succession juBt as we had 
the high waters." 

" This state of things, which must be familiarly known 
to all who have paid any attention to these matters, 
bfflng seen in almost every river that opens into a tide- 
way, ^ves us the most distinct notion of the mechanism 
of the tides. It is a great mistake to ima^e that we 
cannot have high water at London' Bridge (for example), 
unless the water be raised to that level all the way from 
the mouth of the Thunes. In many places that are far 
from the sea, the stream at the moment of high water ia 
down ihe river, and sometimes it is considerable. At 
Quebec it nms downwards at least 3 miles per hour. 
Therefore the water is not heaped up to a level, for there 
is no stream without a decHvity." 

In the river Amazon, the tide is said to ascend against 
the stream, in the manner described, for several days, 
and to penetrate to the distance of 200 leagues from 
its mouth, seven or eight tides, with intenuediate low 
waters, following each other in succession;^ and in the 
Thames we find a similar tidal succession, but not to so 
great an extent, and arising, according to Whewell, 
" from the peculiar circumstance of the river's having a 
tide compounded of two tides arriving by diflferent roads, 
after joume3r8 of different lengths," in allusion to the two 
branches into which the tidal wave is divided on reaching 
the British shores, one of which flows up the Ejiglish 

' BneyUipadta Brilaiutica, Mi. "lUver.'' 



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HTDBOUETtBIC OBSEBTATIONS. 73 

Channel, vhile the other proceeds along the west and 
northern coast of the country, and flowing down the east 
coast, again joins the other branch. 

Such variations on the high-water lines as those 
described bj Bobison would no doubt be found to exist 
to some extent in every situation, if the rise of tide and 
the capacity of the river or estuary were sufficiently 
great to admit of their full development, and if the obser- 
vations made were of sufficient extent to include them 
within their range. But from the smallness of British 
rivers, which flow firom a comparatively narrow and con- 
tracted country, the ordinary surveys made for engineer- 
ing purposes in Britain veiy rarely embrace so great a 
field of observations aa to include the range of more than 
one tide ; nevertheless, even in this country, such irregu- 
larities are found to exist on the tidal lines as to require 
careftd investigation to insure accuracy, especially in situa- 
tions where the rise of tide is great. 

Before entering fiilly on the explanation, of the dif- 
ferent steps to be taken in inak ing a correct series of tidal 
observaticms, by which alone the anomalies I have alluded 
to can be discovered, some preliminary remarks, in expla- 
nation of the exact nature of the inquiry to be instituted, 
appear necessary to the proper understanding of what is 
to follow. 

If the tidal linee of a river were level and parallel, a Natnra or Um 
series of observations on the progressive rise and Ml ofrimtidM. 
HiB tides made at a single graduated gauge placed in any 
part of its course, at which the whole of the tidal rise and 
&11 is developed, would be sufi^ent for correcting all 



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74 



INLAND NAVIGATION. 



soundings and reducing tliem to one level datum line. 
For the person inn.lriTig the soundings on any part of the 
river would only have to note the time of observation, 
and by comparing it with the tide-observations made 
at the same time, as entered in the tide-book kept at 
the gauge, would discover the esact state of ihe tide 
at the time the sounding was made. H, on the other 
hand, the lines had a certain inclination, but were 
nevertheless parallel to each other, the single series 
of observations alluded to would still be sufficient for 
obtaining the correct depths at high water, and con- 
sequently an accurate profile of the bed of the river, 




exhibiting all its ineqxiaUties ; but it is evident that the 
inclination of the tidal lines, and, what is of more import- 
ance, the true position of the bed of the river in reference 
to the datiun line of the section, coxild not be ascertained 
by this means. Thus let the lines a b and c d represent 
the high-water line and the bed of a river respectively, 
and let there be a rise of 1 foot 6 inches in both of them 
in the distance represented in the cut. If one tide-gauge 
only were used, suppose at the lower extremity of the 
river, the section, when protracted, would assume the 
form represented by the dotted lines x h and y d, m 
which the high-water line and bottom of the river are 



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HYDROMETBIC OB8ERVATION8. 75 

shown as being level, whereas their correct positioiis in 
reference to the level line a e, which we may suppose to 
he the datum line of the section, are those repreeented 1^ 
the Hnes a b and c d, on each of which there is a rise of 
1 foot 6 inches. 

The indination of the bed forms an important element Ttda-gftnge*. 
in all questions relative to the navigation of rivers, and 
proper means must be adopted for determining this before 
any design of improvement can be formed, and for this 
purpose it is obvious that at least two tide-gauges must 
be tised, one at either extremity of the river ; and fiirther, 
that their relative levels must he accurately ascertained. 
Now, if the high-water line in the case referred to in 
%. 13 should stand at 10 feet on the lower gauge, it 
will, if their zeros are at the same level, stand at 11 feet 
6 inches on the upper one at the same moment, thus indi- 
cating the difference of level. In this way not only are 
the data for ascertaining the correct depths at high water 
afforded, but a propOT section of the river can be made, 
its tidal lines and bed being represented in their true 
positions in reference to the dattmi line. 

From what has already been said, however, regarding 
the anomalies of the tides, it will readily be seen that it 
would be improper to assume that the tidal lines are 
parallel during the whole period of flood and ebb ; and 
therefore it is necessary to provide for this by adopting 
intermediate stations for tide observations, and by taking 
the soundings of the river at particular periods when the 
deviation firom pazallelism in the tidal lines is at its 
minimum, as will be more particularly noticed hereafter. 



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76 INLAND NAVIQATION. 

stieetion at In determining the number and selecting the sites of 

tidal oburvi- the stations at which tide observationa are to he made, 
the engineer ought to be regulated by the amount of 
tidal rise and the configuration of the banks of the river. 
Where the rise of tide is small, and the tidal currents are 
very languid, few places of observation may suf&ce, but 
where there is a great rise of tide, accompanied by rapid 
currents, the paralleliBm of the tidal lines, on which the 
correctxiess of the soundings depends, is more apt to be 
disturbed, requiring a greater number of points of obser- 
vation. It may be stated, aa a general rule, that the more 
numerous the tide stations are the nearer will the results 
approximate to the exact line of the tidal wave at any 
particular moment of flood or ebb, and the less chance 
will there be of error in reducing the depths of the 
soundings. 
Agenta whieh Whether an extended or limited series of observations 

turb^ in the i^ ^ 1^ adopted, it is necessary, while selecting the sites 
tidd lii^ ^"^^ *^® stations, to have due regard to the agents most 
likely to produce disturbance in the parallelism of the 
tidal lines, such as abrupt turns or bends and sudden 
eDlai^;ements in the transverse sectional areas of rivera 

These variations on the tidal lines, and the manner 
in which they aSect soundings and sections, will be best 
explained by reference to a few examplea 

The results which I shall state, in the first place, 
were obtained from observations made on the river Dee 
in North Wales. 

Three series of simultaneous tide observations were 
made in that river : one at Chester, another at Connah's 



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UVDBOUSTRIC OBSERVATIONS, 77 

Quay, and a third at Fimt, and the following results 
were obtained. 

The distance from Chester to Connah's Quay is 7^ 
miles, and that from Connah's Quay to Flint 3^ miles ; 
the whole distance from Chester to Flint being 1 1 miles. 
The part of the river which extends from Flint to Con- 
nah's Quay may be said to be an open estuary ; and the 
upper part, eztending from Connah's Quay to Chester, is 
an artificial tidal canal, having an unobstructed water- 
way of about 500 feet in breadth at high, and 250 feet at 
low water, as will be seen from the clmrt of the river, 
Plate y. 

The high-water line was found, by an average of 
twenty-four observations, to rise 2 inches from Flint to 
Connah's Quay ; and from Connah's Quay to Chester the 
rise was found to vary from 4 inches at neap to 14 inches 
at spring tides, giving, as the result of twenty-four ob- 
servations, an average rise of 6 inches. The whole 
average rise on the high-water line from Flint to Chests 
is therefore 8 inches. 

The difference between the times of high water at the 
difEerent stations was found to vary very much, and 
appeared to be more affected by the state of the winds 
than by the circumstance of the tides being neap or 
-spring; but the average of the observations gave the 
time of high water at Flint twenty minutes earlier than 
at Connah's Quay, and that of high water at Connah's 
Quay thiri^y minutes earlier iban at Chester ; the whole 
average difference in time between high water at Flint 
and at Chester being fifty minutes. 



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78 INLAND NAVIGATION. 

The average level of the low-water line at Connah's 
Quay ia 2 feet 6 inches below tiiat at Chester, giving on 
the distance of 7^ miles an average &11 of 4*09 inches per 
mile, and the level of the low water at Flint is 7 feet 6 
inches below that at Connah's Quay, giving on a distance 
of 3§ miles an average &11 of 24 '54 inches per mile. The 
total &11 from Chester to Flint is 10 feet, being an aver- 
age £dl on the distance of 11 miles of 10'9 inches per 
mila 

When the rise of tide, as indicated by the Liverpool 
tide-table, is 18 feet on i^e dock sill at Liverpool, the rise 
in the Dee is 20 feet 10 inches at Flint, 13 feet 8 inches 
at Connah's Quay, aad 1 1 feet 5 inches at Chester. 

Plates YL and YIL represrait approximately the forms 
assumed by the tidal lines of the river. Plate VL repre- 
sents the flood lines of a tide rising 19 feet 8 inches at 
Flint. In this, as well as in the other diagrams iUustea- 
tive of the rise or &11 of the tides, the perpendicular linee 
show the relative positions of the stations, and are gradu- 
ated in the same way as the tide -gauges. On the 
horizontal line at the top of the diagrams, the relative 
distances between the stations are marked in miles, and 
at the right side of the Plates, the time corresponding to 
the level of the tide is expressed in hours and minutes. 
The hard diverging lines are drawn through the points at 
which the tide stood at the different stations, as ascer- 
tained by ol»ervation, and represent the tidal linee of the 
river. They are drawn straight, but in reality will pre- 
sent a curved form. Those which are dotted show the 
probahie direction of those lines, when their forms could 



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u- SI- 



o I ^ 




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BYDBOUETBIC OBSERVATIONa. 79 

not, for want of additional tidal stations, be mora ac- 
curately determined. 

The tide, as will appear from an inspection of Plate 
yi., began to rise at Flint at 8 hours 40 minutes ; at 10 
hours 15 minutes it had risen 12 feet 8 inches, and at 
that time had just appeared at Connah's Quay, the sur^ 
&ce of the water at Flint being 5 feet 4 inches above that 
at Connah's Quay. At 1 1 hours 20 minutee the tide had 
risen 18 feet 4 inches at Flint, and was 1 foot above the 
level of the water at Connah's Quay, and 7 feet 10 inches 
above that at Chester, at which place the tide had just 
begun to appear. Thus, while at low water there is a 
&11 of 11 feet from Chester to Flint, there was at the 
time above mentioned a &II of no less than 7 feet 10 
inches on the surface of the water from Flint to Chester. 
At 12 hours 10 minutes It was high water at Flint, and 
at that time there was a &11 of 1 foot 7 inches to Chester; 
but the high water at Chester did not occur till one 
o'clock, by which time the water at Flint had fiJlen 2 
feet 2 inchra, and the fell on the sur&ce of the crater 
fix»m Chester to Flint was 3 feet 1 inch. On referring to 
Hate VIL, which shows the lines of ebb tide on the same 
day, it will be found that the water subsides gradually, 
and that the tidal lines approach much more nearly to 
parallelism and horizontalify than duiiog flood tide. The 
upper line of this diagram corresponds with the tidal line 
when it ia high water at Cheater. 

A similar series of &cts obtained on the Lune in' 
Lancashire, will be found to corroborate generally the 
results deduciUe from those made at the Dee. 



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80 INLAND NAVIGATION. 

The obeervations at the Lime were taken at three 
parts of the rirer, namely, Glasson Dock., Heaton Point, 
and Lancaster Quays, the poEdtions of which will be seen 
on Plate VIIL The distance from Glasson to Heaton is 
3^ miles, and tliat from Heaton to Lancaster 2^ miles, 
making the whole distance from Glasson to Lancaster 
Similes. 

The high-water line at Glasson, Heaton, and I^n- 
caster, was fomid occasionally to stand exactly at the 
same height ; but the average difTerence of level gave a 
£tll of 1 inch from Glasson to Heaton, and a rise of 3 
inches from Heaton to Lancaster, the sur&ce of the water 
at Heaton b^ng slightly depressed, and a small d^;ree of 
concavity on the high-water line observable, due to the 
configuration of the estuary. A great contraction of the 
apace between the banks occurs at Glasson, which checks 
the free flow of the tidal wave, and consequently raises 
its level at that place. After passing this contraction, 
however, the water flows into the large tidal basin or area 
in which the Heaton tide-gauge was placed, extending 
fixim Glasson towards Lancaster, and here the tide level 
again &lls, owing to the much larger sur&ce over which 
the water is distributed. 

The time of high water was fotmd, on eight occadons 
out of twenty-four, to be exactly the same at Glasson, 
Heaton, and Lancaster. The diflerence of time, however, 
between Glasson and Lancaster varied from to 10 
minutes, and the average of the observations gave the 
time at high water at Glasson 3^ minutes earlier than at 
Lancaster ; but this diflerence in time seemed to depend 



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■Ss 



lii i^^ 

> ta. ,£ ^' 

IB I ^ 







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BYBBOHETRIC 0BSBBVATI0N8. 81 

entirely on t^e wind or state of the weather, and not on 
the circumstance of tJie tide being spring or neap. 

The average level of the low water at Glasson is 7 feet 

3 inches below that at Heaton, giving, in a distance of 3^ 
miles, an average &11 of 26 '76 inches per mile ; and the 
average level of the low water at Heaton is 3 feet 9 
inches bebw that at Lancaster, giving, on the distance of 
2^ miles, an average £J1 of 20 inches per mile. Tfae level 
of the low water at Glasson is, therefore, 11 feet below 
that at Lancaster, giving, on the whole distance of 5^ 
miles, a fiJl on the low-water line of 24 inches per mile 
between the two places. 

When the rise of tide, as indicated bj the Liverpool 
tide-table, is 18 feet above the dock all, the rise of tide 
in tiie Lune is 21 feet 1 inch at Qlasson, 13 feet 10 inches 
at Heaton, and 10 feet 2 inches at Lancaster. 

Plates IK. Eind X. represent the forms asaomed by the 
tidal lines of the L\me during a spring-tide which rose 
23 feet 4 inches at Glasson. The tide, as will appear from 
an inspection of Plate IX., began to rise at Glasson at 
9 hours ; at 10 hours 5 minutes it had risen 11 feet 4 
inches, and at that time had just appeared at Heaton ; 
the sur&ce of the water at Glasson being 4 feet 3 inches 
above that at Heaton. At 10 hours 40 minutes the tide 
had risen 15 feet 6 inches at Glasson, and was 1 feot 9 
inches above the level of the water at Heaton, and 4 feet 

4 inches above that at Lancaster, at which place the tide 
had just begun to appear. Thus, while at low water 
there is a Ml of 11 feet from Lancaster to Glasson, there 
was at the time mentioned a &U of 4 feet 4 Inches on the 



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82 jm^ASD NATB3ATI0N. 

Bur&ce of the water from Glasson to Lancsaster. At 12 
hours 20 minutes it was high water at Glasson, Heaton, 
and Lancaster, and at that time there was a ML of a few 
inches both from Lancast^ and frt)m Qlasson to the in- 
termediate station at Heaton, producing the concavity of 
the high-water line already alluded to. 

On referring to Plate X., which shows the lines of ebb- 
tide on the same day, it will be found that the water sub- 
sides gradually, a slight degree of concavity on the sui&ce 
being discernible for an hour and a half after high water ; 
and during the wh(de of the ebb-tide, as in the former 
case, the hnes approach much more nearly to parallelism 
and horizontality than during flood-tide. The upper 
tidal line of this diagram corresponds with that of high- 
water. 

I have feimd in all rivers whose tides I have examined 
with this object in view, that, on comparing the lines 
formed during spring with those formed during neap tides, 
the latter are invariably more nearly parallel to the line 
of high water ; the deviation from parallelism decreasing 
in proportion to the decrease in the rise of tide. For the 
piirpose of illustratiag this, I have given, in Plates XI. 
and XII., an example of the lines formed by the flood of 
a neap tide on the Lune, and the ebb of a neap tide on 
the Dee, which, when compared with the example of the 
spring-tides of these rivers already given, will be found 
to approach much more nearly to horizontality and paral- 
lelism. A further illustration of this is presented in the 
following tabular views of the maximum difference of 
level between the surface of the water at Flint and 



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I 




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■ s i%_ 




n.a,-,7=dbvG00f^lc 



Cheater on the Dee, and at Glasson and Lancaster on the 
Lune, during the flow of tides of various amounts of 
vertical rise : — 

KIVER DEE. 



Dum. 


lUMDfTMa 

raui 


HudrnmnFill 

(rem 
FUattoCli-tw. 


1839. 

H>;31. 

„ 23. 


TkL In. 

14 

15 6 


S 8 
4 6 


, 26. 


16 4 


5 8 


» 29. 
June 10. 


18 

19 8 


6 6 

7 10 



EITEK LnNK 





Rl«QfTW» 


IfutmunMl 


DaTI. 


tt 






OImmh. 


UncMtar. 


1839. 


FNt In. 


r«i Im. 


Aug. 29. 


12 1 


1 1 


„ 31. 


12 9 


1 6 


Sept 1. 


16 4 


2 


„ 3. 


19 8 


2 10 


» 6. 


23 2 


3 2 


,. «. 


23 6 


4 4 



I shall only refer to utother example, which is chiefly 
interesting as showing the undulating lines of the tide- 
wave in its passage up the narrow channel of a winding 
liver. I aUude to the Forth in Stirlingshire, in which, 
from its tortuous course, the tides are somewhat remark- 
able. To give an idea of the windings of this river, it 
may be stated that the distance in a straight line between 



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INLAND NAVIQATION. 



the towns of AlLoa and Stirling, both of which axe situated 
on its banks, is 5 miles ; while by the liver's course it is no 
less than 10^ miles. The tidal currents, howerer, in the 
Forth are not so rapid as those to which I have been re- 
ferring, otherwise the deviations in the tidal liaee would 
doubtless have been much greater thaa they were found 
in reality to be. 

Four stations were selected, namely, at Alloa, Tilli- 
body, Powishole, and Stirling, and the observations were 
made under the direction of Mr. Robert Stevenson. The 
deviation in ihe lines will be seen by reference to the 
diagrams in Plate XIII., which are constructed nearly in 
the same manner as those already described, and represent 
the forms assumed by the surface of the water during 
flood and ebb, at the end of every successive half hour. 
The most anomalous restdt of this investigation occurs at 
Powishole, where the undxilating surface of the water was 
found to rise higher than at any other point on the river, 
either above or bdow it. 

Althoiigh many other series of observations affording 
similar results might be given, it seems unnecessary to 
enter upon them ; my only object being to enable the 
reader to form distinct ideas as to the nature of the 
deviations in the tidal lines, and the several investiga^ 
tions that require to be instituted in mftlfiwg a correct 
survey. The examples I have given, it is presumed, 
aSbrd sufficient in&rmation for that purpose. I shall, 
therefore, proceed to show in what manner and to what 
extent, the accuracy of the soundinga may be affected by 
the non-paralldism of the tidal lines to the line of high 



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i* 




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HYDBOHETRIC OBSERVATIONg. 85 

water ; and, ih&t the observations to be made may be 
clearly understood, I shall, in Hie first place, offer a few 
remarks on the datxam to which the soundings should be 
reduced, and also on the nature and use of the reference 
which is made to the tide-gauges, in the reduction of 
their depths to that datum. 

It is evident that all soundinfrs must be reduced or Datom for 

^ ,j 11 

referred to one datum line, before a correct notion can 
be formed of the depths of water at the places where 
they were taken ; and perhaps the most convenient datum 
is the high water of axL ordinary spring-tide. When I 
had occasion to determine this, I hare taken the range of 
the five highest spring-tides of each smes throughout the 
year (rejecting any abnormal tide due to a storm), and 
adopted the mean of t^ese as the range of an ordinary 
spring-tide. This, however, requires access to a long 
series of observations, which is not often available, and it 
will frequently be found convCTiient to reduce the soimd- 
ings to high water of a spring-tide, having a range of 
16. 18, or 20 feet, as the case may be, at a certain point 
in the river whioh must be specified, and the depths in 
reference to the high water of any other tide, can, with 
this information, be easily ascertained. 

In order to explain the use of the reference which is un of 



shall suppose that a d^th was taken in the middle of' 
an estuary, and that the observer, at the time he made 
the observation, had not any means of asceri>aining the 
state of the tide. Such an oliffiervation would evidently 
be of no practical use, from the circumstance of its being 



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86 INLAND NAVIGATION. 

impossible to ascertain whether the tide had still to rise, 
had attained its full height, or had &llen a certain number 
of feet at the moment it was made, without a distinct 
and accurate knowledge of which, the depth could not be 
reduced to the level of the high water of any particular 
tide. If all the depths were taken exactly at the time 
of high water of the tide to which they were to be re- 
ferred, they would not require any correction ; but it ia 
obvious that in practice this could not be done ; and 
recourse is consequently had to observations of the rise 
and &11 of the tide on graduated gauges, and from these 
the reduction is easily effected. All that is neceasary for 
this piirpose is, to note the time at which the sounding is 
taken, and to ascertain from the tide-gauge record, the 
height at which the tide stood on the nearest gauge when 
the sounding was made. The method of obtaining the 
corrected depth resolves itself into one of three cases, 
depending on the time of tide at which the observation 
was made. It is as follows : — 

Let a lepreaent the deptli of Bomiding made at a certain hour. 
fi the heiglit at whicti the water stood on the tide-gauge 

at the Bame hour. 
f the height to which high water of ordinary epring-tides 

rises oa the gauge. 
S the depth of the sormding reduced to high water. 
Now, in the first case, if /3 is below the level of f, then 

In ^ba second ease, if /3 is on the same level as 7, then 

S=a; 
And ia the third case, which may happen in a high spring or 
equinoctial tide, if /3 is above the level of 7, then 

S = «-C^-7). 



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ETDBOUETBIC OBSERVATIONS, 



87 



These formulfiB would give the true correctionB of the Fommi* onir 
soundings, however &r Touoved from the tide-gauge their ^tion of iidm 
positions might be, if the lines formed by the tidal wave 
were parallel to that of high water at all times of tide, as 
in tliat case the vertical spaces 7— j8 or yS— 7, intercepted 
between t^e high-water line, and the other tidal linee, 
woold be equal throughout the whole of the tidal area 
of the river or estuary. But it has been shown that the 
tidal lines are not parallel, and the formulsa I have given 




maVt tlierefore, under certain circumstances, lead to error. 
As an example of this, I shall take (me of the tide lines of 
the Dee from Plate TL 

Let F and C, fig. 14, represent the positions of Flint 
and Gonnah's Quay Ude-gaugee, and the iatermediate 
point z the place at which the sounding was taken. Let 
F C represent the line of high water to which it is wished 
to reduce the sounding, a b the bed of the river, c d the 
low-water line, and e d the tidal line which existed when 



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88 INLAND NAVIGATION. 

the observation was made, which is not imagioaiy, but 
will be found to correspond with that at 10 hours 15 
minutee, as represented in Plate VL Further, let the 
sounding x y =8 feet. Let the depth at high water 
zy ei the position of the soimding, as measured on the 
diagram, = 17 feet 4 inches. Let the rise of tide at 
CJomiah's Quay g d = 12 feet 5 inches, the rise of tide at 
Flint cf= 19 feet 8 inches, and the height at which the 
water had risen on the Flint gauge, when t^e sounding 
was made, e c = 12 feet 8 inches. Now suppose the 
sounding is to be reduced by a reference to Gonnah's 
Quay ; according to the foregoing formula we should have 

zy=xy + {ffd~0) 

= 8'+(12*5-0) = 20feet 5 inches, 

the depth at high water, instead of 17 feet 4 inches, 
giving 3 feet 1 inch more than the actual depth, an error 
which might lead to unpleasant consequences, both as 
regards the navigation of the river and the framing of an 
estimate of works for its improvement. Again, if refer- 
ence were to be made to Flint, we should have 

zy~xy+fc—ec 

= 8'.+(19'.8-12'.8) = 15 feet, 

the depth at high water, instead of 17 feet 4 inches, being 
an error of 2 feet 4 inches. 

Now, the case that has been taken, which, in ssry view 
of the subject, would involve an error in the depth, either 
of 3 feet 1 inch, or 2 feet 4 inch^, is not the worst that 
may be cited, for, tmder certain circumstances, and in cer- 
tain situations, the error would be considerably greater. 



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HYDBOHETBIC OBSEBTATIONS. 89 

Nor, indeed, are the high-water depths iAxe only 
results that would be affected. The correctness of the 
Bection of the bed of the river, the depths of the sound- 
ings when reduced to low water, and die heights of the 
sand-banks above the low-water line, depends entirely on 
the accuracy of the high-water depths. It is obvioiisly of 
great importance, therefore, that the engineer should not 
only be fully aware of the cause of these errors, and the 
extent to which the results of a survey may be afEected 
by them, but also that he should know, uid be able to 
ap|dy, where necessary, the means by which they may be 
neutralized. 

It haa been shown that the erroneous results alluded QaunimiM 
to arise from the non-parallelism of the tidal lines to the k " 
line of the high water to which the soundings are to be 
reduced, and it has been stated that the most effectual 
means of avoiding inaccuracy from this cause is to increase 
the number of gaxiges ; but even this precaution, unless 
carried to an extent which may, in ordinary practice, be 
safely regarded as quite unattainable, wotdd not produce 
the desired effect. The only really practicable cure whidi 
can be applied is that of taking the soimdings when the 
lines are most nearly parallel to the line of high water. 
That there are not only certain tides, but also certain 
periods of every tide, when this approach to parallelism 
is much more near ihan at other times, has, it is presumed, 
been clearly established ; and in accordance with this I 
gave in 18'42 rules for direction in making the soundings, 
the correctness of whidi I have had repeated oppotiunitiea 
of practically testing. 



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90 INLAND NATIOATION. 

First, Soxmdings made in the immediate vicinity of 
the gauge, by a referenoe to which they are to be cor- 
rected, are not appreciably affected by deviatioiis from 
parallelism, and may be taken at any time of tide, and 
tmder any circumstances. 

Second, The farther distant the positions of the sound- 
ings are from the gauge, by a reference to which they are 
to be corrected, the greater is the chance and the amount 
of error which may arise from uon-paralleliam. 

Third, Soundings should be made during neap in pre- 
ference to spring tidea 

Fourth, Soundings should be made in ebb in prefer- 
ence to flood tides. 

Ft/i^ Soundings to be taken in flood-tides, especially 
during springs, should not be made till within about an 
hour of high water. 

If these precautionary rules be kept in view, they will 
be found to coimteract in so great a measure the effects 
of non-parallelism as to insure in most cases sufficient 
accuracy for all practical purposes, in reducing the obser- 
vations. They apply most particularly to rivers in which 
the rise of tide is great and the currents are strong ; but 
they may be said to be applicable, in a greater or lees 
degree, to bM situations, and may be embraced in these 
two directions, a compliance with which does not seem to 
involve any great difficulty : First, soundings should not 
be made during very high tides ; and secondly, all dbser- 
vatioTis not made cAout an hour before and 'q/ier high 
water should be confined to the immediate vicinity of fAe 
gauge by a ref^ence to which they are to be corrected. 



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HYDEOMETEIC OBSEEVATIONa 91 

In addition to the soundings which are taken through- 
out the area of an estuaiy during flood or ebb tide, it ia 
useful to take a series in the navigable channel at low 
water. The soundings belongiDg to the first class are to 
be reduced to the high water of ordinary spring-tides by 
the formula given at page 86 ; those of the second or low- 
water seriee require no reduction, unless the level of the 
water on the gauge shows that the river was in flood, 
and when all of i^em have been laid down on tlie chart 
we shall have the high-water soundings distributed over 
the several sfmd-banJiB throughout the area of the estuary, 
and also a line of low-water soundings in the centre of the 
navigable channel, as shown in the chart of the Lune, Plate 
Yin., on which the soundings have been marked as an 
illustration. But it is still necessary to ascertain the 
heights of the sand-banks above low water. For this 
purpoee, the rise of the tide at different parta of the river 
must be ascertained ; whidi, together with the determi- 
nation of the height of the sand-bankB above the low- 
water mark, is done in the following manner : — 

From the system followed in taking the soundings High ud low 
which I have described, it is evident that a high and a lug*. 
low water sounding nearly corresponding in position can 
generally be obtained at all the places where the lines of 
soundings, which have been taken during flood or ebb 
tide, cross the low-water channel This will be easily 
understood by referring to the chart of the Lune, al- 
though, from the smallness of the scale, the exact Unee in 
■which they were taken are not very definitely exhibited. 
Let a, therefore (without reference to the Plate), represent 



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92 INLAND NAVIGATION. 

a high-water aoundiug (corrected by the formula ^ven at 
page 86) whose position is in the naTigable channel, and 
let J3 be the low-water sounding which moat nearly coin- 
cides with the position of a. Then a~ will be the 
Tertical rise of tide (which we shall call y) at that point. 
The values of y being thus found at as many points as 
possible in the channel of the river, the number of which 
points will be limited by the number of the lines of high- 
water sounding that cross the low-water channel, they 
should be marked on Uie plan in laige figures, as shown 
Fonmu tor in the chart of the Lune already referred to. Now tiie 
TiHoftid«uid values of the soundings a a a, etc., distributed throughout 
ImhIu. the estuary, will either be equal to, greater, or less than 

those of 7 7 7, etc., which we may suppose to represent 
the vertical rise of tide at the points nearest which the 
soundings occur, and the three results may be expressed 
as follows : when 

a — 7 = n, 
the sounding has oocurred in the navigable chamiel or 
some deep pool in the sand-banks, and n = the depth at 
low water ; when 

7 = o, 

the soimding has been made exactly at the edge of low 
TKiter, or perhaps of a pool on a level with low water, as 
t^e case may be ; or, in other words, at tiie point where 
the level of low water cuts the sand-bank ; and when 

y — a = n, 
or, as it is marked on the chart, — n. 

iha sounding has occurred on a sand-bank or other raised 



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HTDROMETMC 0BSEEVATI0N8. 93 

obstouction, and — n = tlie height of the bank above low 
water. In marking these soundings on the plan it is 
necessary to show the depths both at high and at low 
water, and the most convenient way of doing this is to 
put them in a fractional form, the depths at high water 
being placed aa the numeratdr, and tLose at low water as 
the denominator, distinguishing the heights of ihe sand- 
banks above low water by prefixing the negative sign. 
According to this notation the three results alluded to 
would be stated thus on the plan : — 



according as the sounding had been taken in the low- 
water channel, at its edge, or on the top of a sand- 
bank. 

For an example of this, Plate YIII. may be again 
referred to, where, at a place marked Baffl^i^ord, nearly 
opposite the needle of the compass, it will be observed, by 
the large figures at the side of the channel, that the rise of 
tide is 12 feet 9 inches. It will also be seen that, at the 

middle of the channel, the sounding -^^. " ^11^ occurs, which 

denotes the depth at high water to be 18 feet 9 inches, 
and that at low water 6 feet, the difference between the 
two quantities being 12 feet 9 inches, which is the rise of 
tide at that place. On the adjoining sand-bank there 

is a sounding, _ „tL iaib. ? denoting the depth at high 

water to be 9 feet 11 inciies, and t^e height of the sand- 
bank above the level of low water to be 2 feet 10 inchea 



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94 INLAITD NATIOAITON. 

The same notation will be perceived throughout the whole 
of tte chart of the Lune. 
crowtectioiu, In addition to the soundings, it is very generally 
necesaajy to make cross sections and borings of the river's 
bed to ascertain the quantities and quality of the mate- 
rials to be excavated in order to obtain a certain depth of 
water. 

In selecting the points at which to make these obser- 
vations the engineer must of course be guided by the 
object of tiie invesUgation and the fermation of the river's 
course. If there be fords or shoals in the bottom which 
occasion obstructions to the navigation, and require to be 
removed, one or more lines of section may be fixed on at 
each shoal, according to its extent. Where, as sometimes 
happens, the channel is irregular, or has rock occurring at 
various points, it is often necessary to obtain, by means of 
numerous cross sections, an exact survey of the whole, or 
at least of a great part of the bed, before any distinct plan 
of operations can be formed; and the depths of the 
sections and borings may be referred to the same datum 
as the soundings of the depths of water. 
Ut. uitoheiri Mr. Henry Mitchell, of the United States Coast 

iniiii4 Bievk- Survey, who has published several interesting papers on 
ti^ri^' Marine Surveying, has proposed an ingenious method of 
jj^j]^ determining elevations along the course of a tidal river 
without the aid of a levelling instrument, which he 
explmns as follows : — " Set up graduated staves at such 
distances apart that the slacks of the tidal cun^nts ^all 
extend from one to another. By simultaneous observa- 
tions ascertain the difference in the readings of those 



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HYDBOMSmUC 0B8SBTATI0NB. 



gauges at die eJack between ebb and flood currraits, and 
again the difference at the alack between flood and ebb, 
then apjdy the rule : The difference in the elevations of 
the zeroa of the gauges is egucU to one half the sum of the 
differences of their readings at the ttoo slack waters. 

" In the Hudson I found that staree 10 miles apart 
could be ref^red to each other by t^ rule, and ih&t no 
nice current obserraticms were really necessary. The 
slope is BO nearly constant about the time of slack water 
that an error in this time of a half hour, in some cases, 
would be of no consequence. The coincidence of time at 
the two gaug^ and the careful reading of the heights are 
the most important elements. I ofier below an illustra- 
tion from observations upon one of the fourteen reaches 
examined during October 1871 ; — 





BU«k.« 


bh to Mood, 




81>ok,nao4(oBbb. | 


Ttau. 


'SS£ 


P»SS. 


DlOtomo^ 


Tint. 


»«»" 


P,;SRKf. 


D»»«. 


B. K. 
10 20 


rtA 
207 


F*«t 
2-86 


0-79 


B. B. 
4 45 


p»t 
4-24 


Foot. 

6-73 


FMt 

1-49 


10 25 


218 


2-97 


0-79 


4 50 


4-20 


5-66 


1-46 


10 30 


2-27 


307 


0-80 


4 55 


412 


5-60 


1-48 


10 36 


2-34 


317 


0-83 


( 00 


403 


5-63 


1-60 


10 40 


2-47 


3-27 


0-80 


5 05 


3-99 


6-48 


1-49 


10 U 


2-64 


3-30 


0-82 


5 10 
5 16 
5 20 


3-93 
3-88 
3-88 


5-40 
6-36 
6-29 


1-47 
1-47 
1-49 


080 


1-48 



\ (b — a)— 0-U — dope of KtifMM at iljuik mtcr." 

It is obvious that this method of treatment 



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96 INLAND NAVIGATION. 

that the slope on the sur&ce of the river during the alack 
of the e66-tide is exactly equal in the opposite direction 
to the slope during ih.e slack of the^cxi-tide ; that the 
section lines formed hj the flowing and ebbing tide at 
these periods are extremely regular, that ihe gradients 
between the points of pbservation are uniform, and that 
tiie tidal lines during the period of observation are prac- 
tically parallel la the river Hudson the tidal range, 
though only about 5^ feet at New York, is felt for a dis- 
tance of 150 milee, as &r as Albany, and the tidal lines 
have gentie gradients, and in that case Mr. Mitchell has 
foxmd the method to be applicable ; but a glance at the 
tide lines in the preceding Plates will show that it could 
not be applied to such rivers as I have been speaking of, 
where I suspect nothing short of actual levelling of the 
gauges will insure such a result as can be relied on. 



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CHAPTER V. 

DISCHABGB OF BITERS — ^tJNDEB-C0RBENTa — SPECIFIC 
QBAVITIES OF WATER, ETC. 

Diacharge of riven — Mode of detennioing the velocity of ft river ; by floati ; by 
taohoincter — Fonnnla for redneiag the itirfttce to netui velocity— Hethodi of 
aaoertaimng duchsrge by f omrnlie — FormalBe geneT&Ily (Lpplicable, but mffording 
only In ■pproziinBtioa — Flooda—PUohKTge shoold be ascertaJDed in noRDal 
condition of atream — Method of gMigiog average diachaige, exdnaive of flooda 
— ReanHa of formuln deatroyed whwe onder-cDrreDta eiiat — Inib^menta for 
aaoertaining nudei^onrrenti — Tat^ometer — Duder^nrreut float* naed at Cro- 
marty Slrth ; in deap-aea reiearohBa, etc. — Canse of nnder-civranta — Metbodi 
of aaoertaiiiiiig apedmeoa of water from different deptba — IHfferent forma of 
bydrophorea, and mannar of using then — Oocvnence of freab water in the aea 
— Specific gravitieB of freah and salt water. 

It is often necesaaiy in the practice of engineering to 
determine the dischai^ of rivers, and the velocity and 
direction of sur&ce and under currents. In some inves- 
tigations, also, it is desirable to ascertain the quality of 
water taken from 'rorious depths and at different times of 
tide, so as to know the proportions of sea and fresh water 
which constitute the mixture, and the quantity of solid 
materials held in mechanical suspension, such as sand or 
mud. 

A few remarks on the mode of conducting these dif- 
ferent investigations will form the subject of this chapter. 

The most accurate method of measuring water dis- 
charge is to construct a gauge-weir and ascertain the 
quantity of water flowing over it ; but as this process is 



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98 nOAlTD NAVIGATION. 

only appliobble to small streams, it does not come within 
the scope of our subject. 

The discharge of a river is generally ascertained by 
multiplying its mean velocity by its sectional area ; and 
in gauging a river with this object in view, it is necessary, 
first, to determine accurately its sectional area in a plane, 
as nearly aa possible at right angles to the direction of the 
current. This is done by selecting a place where the 
banks are regular and the stream tranquil A graduated 
cord is stretched across, as nearly as possible, at right 
angles to the direction of the currents. The depths of 
water are carefully taken, with a rod grsiduated to feet 
and inches, at distances of 5 or 10 feet (as indicated by 
marks on the cord), according to the minuteness of the 
inquiry to be instituted or the irregularities of the river's 
bed, and, &om the data tlius obtained, an accurate cross 
section showing the sectional area of the river can be 
constructed, 
uode et Mitr- After && observations for the cross sections have been 

mining tlwTalo- iii <. ..,,. 

d^ofAiinr. Completed, the measurements for ascertaining the veloaty 
should at once be made before any change in the level of 
the water, and consequent cJiange in the area, can take 
place. The velocity with which the water passes over 
tiie bed of the river will be found to vaiy, gradually 
decreasing Scorn the fiur-way or deepest part of the river 
towards the sides, and from tiie sur&ce towards the bottom, 
except in certain exceptional cases, to be afterwards 
noticed. For the purpose of calculation, tiiere&re, the 
mean vdocity must be determined. This is most accu- 
rately done by ascertaining the sur&ce velocity in the 



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DIBCHABOB OF BITERS. 99 

middle of each of the compartments into which the trans- 
Terse section of iJie riTer is dirided, by the soundings 
made, as already explained, and from these sur&ce Telo- 
citieB, by a simple formula, tbe mean Telocity of each of 
the compartmeDts can be obtained, and the mean of these 
will be the reqiiired mean Telocity of the riTer. 

For the purpose of ascertaining the surfitce Telocities, 
various methods may be'employed. 

The most common, but by no means the mostBjft 
satis&ctory, mode of proceeding, is to drop into ^e 
water, from a boat, a float (whose specific gravity 
is merely great enough to sink it to a level with tbe 
surfiice), at a point about 30 or 40 feet aboTO the line of 
section, so as to insure its acquiring the full T^ocity of 
the current be&re it reaches the cord^ An observer, 
stationed at the cord, notes exactly the moment at which 
the float passes, and follows it down the stream till he 
reaches the line of two poles, which have been fixed in re- 
ference to the observations, when he agfdn notes the exact 
moment of its transit at the lower station. The dapsed 
time between the two transits is then noted in the book, 
along with the distance between the two places of obser- 
vation, which, owing to the irregularity of most rivers, 
with regard to width, depth, and Tdocdty, can seldom be 
got to exceed 100 feet. This operation has, of course, 
to be repeated for ereiy compartment of the cross 
section. 

Dr. Anderson, in measuring tiie discharge c^ the Tay, 
at Perth, used an adjustable float, which extended fi«m 
the Bur%;e to near the bottom of the river, and so 



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100 INLAND NAVIGATION. 

obtained at once, approximately, the m&xn velodty of each 
compartment of the cross section of the stream. 

Certain disadvantages attend the method of measur- 
ing velocities by floats, ■which render it not generally 
applicable. For eiample, it is only adapted to rivers of 
limited breadth, owing to the impossibility of an observer 
being able to discover with sufBcient aocuracy the exact 
time when the float passes the std>tion lines, if it be viewed 
fix>m a distaace, as, for example, &om the bank of a 
broad river. There are, however, greater objections than 
this, which, when pointed out, will be sufficiently obvious 
to every one. In any part of {h» river's bed passed over 
by the floats, the slightest irregularity of the bottom pro- 
duces a disturbance in the motion of the stream, and 
alters the velocity, so that it is not possible, from the time 
occupied by the passage of the float over the measured 
distance, to deduce the mean velocity at the line of cross 
section. It is also impossible, by this method, to obtain 
a sufficient number of distinct and independent obser- 
vations, apphcable to each division of the stream, as the 
eddies and irregularities of the current which exist in aU 
rivers, generally cause the lines passed over by the floats 
to cross and interfere with each ot^er in such a manner 
as to destroy all connexion between any given series of 
observations, and the several compartments of the river, 
whose mean velocity they were intended to ascertain. 

The great object is to determine the velocity of each 
portion of the stream, as it passes the line of cross 
section ; and the best way of doing this is to employ the 
tachometer or stream-gauge — an instrument of great ser- 



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DISCfiABQE OF RIVERS. 



101 



vioe in such inquiries. The current impinging on a vane 
causes it to reTolve, and the niunher of revolutions made 
by the vane being registered on an index, which is acted 
on by a set of toothed wheels, indicates the velocity of the 
current. 

The construction of this instrument, and the manner ihMciiptioii or 
in which it acts, will be best described by a reference 




to fig. 15, which is drawn to a scale of one-third of 
the ftiU size. In this view, y/ represents the driving 
vane, which is acted on by the stream, and of which g 
is a plan. The plane of this vane is twisted, as repre- 
sented by the dark shading in the cut, so as to pre- 
sent, not a knife-edge, but an oblique &ce to the action 



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102 INLAHD KAVIGATION. 

of the current, which, by impinging on it, causes it to 
revolve. On the spindle or shaft of this vane, aa endless 
screw is fixed at e, which works in the teeth of the first 
registering wheel, and causes it to revolve, when the vane 
is in motion, and the screw in gear. Letters a and h re- 
present a bar of brass, to which the pivots on which the 
registering wheels revolve are attached. This bar is 
moveable on a joint at h ; and at the point a, a cord, a c, 
is fixed, by puUiog which the bar and wheels can be 
raised, and on releasing it they are again depressed by a 
spring at d. When the bar is raised, the teeth of the 
wheel are taken out of .gear with the endless screw, and 
the vane is then left at liberty to revolve, the number of 
its revolutions being unregistered ; but when the cord is 
released, the spring forces down the wheels, and immedi- 
diately puts the roistering train into gear, in which 
state it is represented in the cut. Letter ^ is a sta- 
tionary vane (which is shown broken ofi^ but measures 
about 9 inches in length) for keeping the plane in whidi 
the driving vane revolves at right angles to the direction 
of the current, and h is the end of a wooden rod to which 
the tachometer is attached when used. The different 
parts of the instaniment itself are made of brass. 

The moveable bar for the registering wheels and the 
api^cation of the cord and spring whidi have been de- 
scribed, afford the means of observing with great accuracy 
in the following manner. The instrument having been 
adjusted by setting the registering wheels at zero, or 
noting in the field-book the figure at which they stand, 
the cord is pulled tight, so as to raise them out of gear, 



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DISCHABGE OF BITEStS. 103 

and the mstrument is Uien immersed in ihe water. The 
vane immediately begins to revolve by the action of the 
current, and is permitted to move fi'eely round until it 
haa attained the iulL velocity due to the stream, when a 
signal is given by the person who observes the time, and 
the r^istOTing wheels are at that moment thrown into 
gear by letting the cord sKp. At the end of a minuie 
another signal is given, wheu Ha eord m again drawn 
and the wheels taken out of gear, and on raising the in- 
strument from the water, the numb^* of revolutions in 
the elapsed time is read off This observation being 
made in ihe centre of each division of the cross section, 
the number of revolutions due to the velocity at each 
part of the very line where the cross section is taken is 
at once obtained. 

Before using the tachometer, it is obvious that the 
value of a revolution of the vane must be ascertained ; 
and although this is done l^ the manu&cturers, it ia 
proper that the scale of each instrument should be deter- 
mined by the person who uses it, and that it be tested 
if the instrument has been out of use for some time, 
before being again employed in making observations, 
A scale sufBciently accurate for most hydrometric pur- 
poses may be obtained by immeiBing the instrument in 
some r^ular channel, such as a mill-lead formed of 
masonry, timber, or iron, where the velocity is nearly the 
same throughout, and noting the number of revolutions 
performed during the passage of a float over a ^ven 
number of feet, measured on the bank. This number, 
therefore, becomee a constant multiplier, and the number 



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104 INLAND NAVIGATION. 

of revolutions being detennined, the number of feet 
passed over by the water in the given interval of time 
is ascertained. 

The raluee of the revolutions may perhaps be more 
accurately determined by placing two stakes 100 feet 
apart on the banks of a canal. The gauge, attached to 
a rod having a knee or bend at its extremity, is then 
immersed at a little distance from the stakes, and drawn 
quickly through the water, so as to cause the vane to 
refvolve. On passing the first stake the cord is slipped, 
and the r^;istration commences. On passing the second 
stake the vane is taken out of gear, and the number of 
revolutions made in passing over the distance of 100 
feet gives their value. The operation is repeated several 
limes, alternating the direction in which the gauge is 
moved through water, to destroy tJie effect of any small 
current that may possibly exist, and the mean of the 
observations is adopted to calculate the scale of the in- 
strument. 
Formnu far Having thus bv mofms of the tachometer determined 

redndngOie . 

•nrfaceto meio the suifiice Velocity of the river at each of the divisions 
of tlie extended cord, the next step is the reduction of the 
observed surfiwe to those of mean velocities, which will 
be readily done by the following rule of Du Buat. 

It is not clear that Du Buat meant this formtda to be 
applied in the maimer here described ; on ihe contrary, it 
rather appears that he meant to deduce from a single 
surfiice velocity taken in the centre of the stream a mean 
velocity applicable to the whole sectional area. He, as 
quoted by Professor Robison, says, " The mean velocity 



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DISCHABOE OF RIVEBS. 105 

in anj pipe or open stream ia the arithmetical mean 
between the velocity in the axis and the velocity at the 
Eudes of a pipe or bottom of an open stream ;" but it is 
hardly possible to find a liver with a cross section so 
symmetrical as to admit of a single central obeervaiion 
proving sufficient, and the formula is therefore often ap- 
plied to <^e velocities as measured in the centres of the 
different copipartments into which the river is divided in 
making the cross section. Ihi Buat's rule referred to is 
as follows : — 

If unity be taken from, the square roof of the surface 
velocity expreaaed in inches per second, the square of the 
r&mioinder is the velocity at the bottom, and the fnean 
velocity is the half sum of these ttpo. 

Thus, let a = the observed sur&ce velotdty, 
„ j9=the bottom velocity, and 
„ Y=the mean velocity, all in inches per second. 

;8=(V.-l)'and7=e±^j 

and hence, tie mean velocity is diiectly deducible from 
the sur&ce Telocity by the following formula : — 

The mean velocities obtained by calculation are to be 
multiplied into the area of the spaces in the centres of 
which the observations were made, in order to obtain the 
cubic contents of water dischai^ed in each division ; and 
to obtain t^e whole discbEuge, it is only necessary to add 
together the results of tiie observations made in all the 
different compartments. The apportioning of the stream 



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106 INLAND NAVIGATION. 

into different parts, and treating each as a sepftiate 
channel, appears to insure a much greats probability of 
a correct measurement than any metiiod which depends 
upon assigning to the whole area a common velocity ; and 
it is obvious that this method can be efiectuaUy followed 
only by the use of the tachometer described, or by any 
aimilax instrument which possesses the advantage of con- 
fining its indications to the spot where the sectional area 
of the river is actttally measured. Wherever, as will 
frequently happen in regular streams, the velocity of 
several compartments, as ascertained by the stream-gauge, 
are found to be t^e same, the areas of these compartments 
may be added into one stun and multiplied by the common 
vdocity. It seems neceesaiy to observe that velocities 
exceeding 3 miles an hour are apt to injure an instru- 
ment of the az» and proportions shown in the cut, and 
that in gauging more rapid rivers an instrument on 
the same principle, but of stronger make, should be 
employed. 

The velocity of currents in the open sea or in estuaries 
may also be detemiined from a boat at anchor, by allow- 
ing a float to run out during a given interval of time, and 
observing the quantity of graduated line which has berai 
let out. Some of the various forms of roistering logs are 
also very suitable for such experiments when the velo- 
cities are not below 2 miles an hour. 
Method* or But as the numerous observations of velocities which 

duoUige bj I have desoibed always occupy much time, many formules 
have been proposed to shorten the work of calculating the 
disdiarge of a stream. I have had opportunities of test- 



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DIBOHABQE OF RITEBS. 107 

ing the value of these formulsa by cx>mparizig the results 
th^ gave with those obtained, by the more earful and 
elaborate process which I have desciibed, and as these 
gen^nlly recognised formulss are conflicting, and in aome 
cases inaccurate, I shall give the result for the informa- 
tioQ of the student. 

Before doing bo, however, it is neceesaij to define and 
explain certaia terms, without which the s^plicatian of 
the different formulse would not be intelligible. 

In dealing with the discharge of a liver, we are to 
understand : — 

First, That the slope is the fidl on the sur&ce of the 
water, and is generally expressed in feet per mile, and is 
ascertained by levels carefully taken. 

Second, The sectional area is the width multiplied by 
its average depth, as ascertfuned by means of the section 
ahready explained at page 98. 

Third, The hydratdic mean depth is the quotient 
given by dividing the sectional area of the channel in 
square feet by the wetted border or perimeter in lineal 
feet, also ascertuned fix»m the section. 

Fourth, The mean velocity, which may either be de- 
ducted from the sur&ce velocity by formuhe, or ascer^ 
tained direcUy by measurement, is that velocity which is 
used in ascertaining the discharge. 

Fifth, The discharge is the quantity of water yielded 
1^ the sh^am in a given time, and is generally stated la 
cuHc feet per minute, being the mean velocity in feet 
'per minute multiplied by the sectional area in square 
feet 



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108 INLAND NATIGATION. 

The formulae which I subjected to trial were : — 

I. Formula given by Dr. Bobiaon, founded on Du 
Buat'a inveetigationB ;' — 

. VS - Hyp. log. of VS + 1-6 ^ ' 

in whicli M = the mean velocity in inches per second, 
d = the bydranKc mean depth in inches, 
S = ihe leciprocal of the slope of the surfiice which is 
the denominator of the fraction expressing the 
slope, the nnmerator being always unity (a slope of 
1 foot a mile ia tAiti therefore 6280 = reciprocal 
for that slope). 
Hyp. 1<^. as the common log. of the number to which it ia 
attached, mnltipUed by 2-3026. 

II. Formula given by Sir John Leelie :' — 

in which M b the mean velocity in miles per hour, 
a = the hydraulic mean depth in feet, 
/ = the Call on the surface in feet per mila 

IIL Formula given by Mr. Ellet for calcula^g di»- 
dia^ of ihe Mississippi :' — 

M = 0-8 T 
in which Y = the surface velocity in feet per second, 
d = the maximum depth of the river in feet, 
/= the fall on the sur&ce in feet per mile, 
M = the mean velocity in feet per second. 

' Seeuiide " Rrnr," £«q/dopadia BritaMtita ; ftUo .J S^Mem iff MtehanUal 
PKUotopk]/, bjr John Robiiim, toL ii. p. 4S3. 

* Ekme»U'<^Nalnna PhUoeapAy, bj Prof. Ledie, Edinburgh, 1829, rol. L p. 423. 
■ The iflMiHippi and Ohio Ritert, by Chwle* Elkt, Philadelphia, 1853. 



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DISCHABOE OP RrTEB& 109 

rV. Formula given in Mr. Beardmore's tables :' — 
M = Vfl'2/ X 66 
in which M = mean velocity id feet per miaate, 
a = hydraulic mean depth in feet, 
/= fall per mile in feet. 

Y. In addition to these formulEe, the vriter also sub- 
jected to trial the formula of Du Buat, as given at 
page 105 : — 

2 
in which M = tiie mean velocity in inches per second, 

y =3 the maximum surface velocity in the axis of the 
stream in inches per second. 

In order to compare these different formulse, a vexj 
fiivourable situation was selected for ascertaining the dis- 
charge of a stream by care&l measurements of its sectional 
area and of the Telocities at di&rent parts of its sur&ce 
from the centre to dther side with the ta^ometer, as 
described at page 102, and the result gave a dischaige of 
1653 cubic feet per minute, which, from various measure- 
ments, I believe to be a very near approximation to the 
actual dischai^ The slope was also accurately ascertained 
by careiul levellings, and tiie following are the results : — 

CDbiefeet. 

Dischaige from measurement as above, 1663 per minute. 

1st, By Bobison's formula, . . 2214 do. 

id. By Leslie's do. . . . 2474 do. 

3d. By Ellet's do. . . . 2784 do. 

ith, By Beardmore's do. . . . 2336 do. 

Stk, By formula assuming the mean de- 
duced &om the centre surface velocity 
astlie mean for the whole section, . I960 do. 
^ Ugdraulit Tahk; by Nathaniel Bewdmore, C.E., London, 18&2. 



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110 INLAND NAVIGATION. 

It will be seen from this statement, that none of the 
formulee afford a near approximation to the diBchai^ of 
ike Bmall stream to which they vrere applied. 

Again, it was ascertained by the late Dr. Anderson, 
of Perth, after ' moet carefrilly dividing the cross section 
into compartments, and ascertaining the velocity of the 
stream in each of them, by the metiiod described at page 
99, that the dischaige of the main branch o£ ihe Tay at 
Perth'was 147,391 cubic feet per minute.* I ascertained 
the dischaiges, as calculated by the different formulse as 
above, and the following are the results : — 

Cnbiofaet. ; 

Discharge per measurement, by Dr. 

Anderson, 147,391 per minute. 

lif. By Bobison'a formula, . 163,632 do. 

2(2, By Leslie's do. . . . 166,134 do. 

3<I, ByEllefa do. . . . 122,002 do. 

itk, By formala in Beardmore'a tables, 156,669 do. 

nth, By formula assuming the mean de- 
duced &om the centre surface velocity 

as the mean for the whole section, . 179,237 do. 

FomoiagMMr- The result of these trifilB, and others which I have 
bat^rding ' had occafidon to make, is, l^t none of the formuls that 
have been proposed will be found genercJIy i^licable ; 
but t^e following formula may be applied, and will, in 
most cases, give a pretty near approximation to the velo- 
city and discharge due to a given area and &11, viz. : — 



' TUa doM not inoluda th* Willowgftte nor th« Eani. 



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DISCHABOE OF BIVEBS. Ill 

ia which x s the mean velocity of the whole section of the stream 

in miles per hour, 
y = a quotient which is found to vary from 066 for small 

streams under 2000 cuhic feet per minute, to 09 

for lai^ rirers, siich as the Clyde or the Tay, 
a = the hydraulic mean depth in feet^ 
/ =3 the fall on the surface in feet per mile, 
e ss the mean velocity of the whole section of Uie stream 

in feet per minute, 
s = the sectional area of the stream in feet ; and 
D = the discharge in cuhic feet per minute. 

It muat stUl be kept in view that the application of 
any known formula to the detennination o£ the mean 
Telocity and dischai^ of a river ia shown, by experi- 
mental inquiry, to afford only a rough approximation; 
unless observations are made embracing the velocitiee at 
different parts of the cross sectional ar^ in the manner 
already described at page 98. 

In order to render the measurement of dischaige nmOM. 
useiul, care should be taken, when the stream is gauged, 
to ascertain that it is in a normal condition, by which is 
meant that it is neiUier dried to its minimum by a long 
drou^t, or swollen to its maximum by heavy rains. The 
stream in this normal condition is said to be in its state 
of ordinary summer water, or at its ordinary summer 
water level, and to he unaffected by l<mg droughts or by 
heavy rainfall 

It is obvious that it is not possible to oSlsr any direc- 
tions for determining when a stream is in this normal 
condition, but it will generally be found that the resi- 
dentfi on its banks, particularly those engaged in its 



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112 INLAND NATIOATION. 

fishings, if there be any, can tell when the water is at 
ordinary aummer level. The fluctuationfi of a river from 
its lowest to its highest state are excessively capricious, 
the amount of flooding which is ascertained to take place 
in difierent rivers having no constant ratio either to the 
summer water whidi they discharge or to the area 
drained hy them. This, indeed, does not seem surprising 
when we consider the very different character, both geolo- 
gically and agriculturally, of the districts through which 
rivers flow. The drainage area in one situation may 
include lai^ tracts of hill country, having steep and 
scantily soiled slopes, from which the rain is readily dis- 
charged ; in another place it may be flat, or gently rising 
deep soiled agricultural land absorbing much of the rain 
that &lls, and giving it off only by slow degrees. Other 
districte are more or less affected by their geological for- 
mation — some strata being less absorbent than others. In 
otiiers, again, agricultural improvements have an influence 
on the drainage — sheep-graziDg land being less absorbent 
than arable land. In rivers whidi flow from lakes a 
reservoir is afforded for the storage of siirplus crater, 
which checks the floods below. But again, as in the case 
of the Tay, which flows from Loch Tay, a sheet of water 
fourte^i miles long and three-quarters of a uule broad, it 
is &imd that in gales of westerly wind accompanied by 
heavy rain the lake water is heaped up at the outlet, and 
greatly increases the flood in the river ; so that even in 
the recurrence of floods themselves there are many cir- 
cumstances which vary their effects, even in the same 
district. The heaviest floods in all rivers occur with 



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D18CHAB0E OF BIVIIBS. 113 

heavy rain and melting snow, for then the hed of the 
river has, it may be said, to dischai^ a compound flood 
made up of melting snow and &lling laizu 

The construction of rtulwajB in India has afforded in- 
teresting information as to the floods of the great Indian 
rivers, which are fully discussed in papers hy Lieutenant- 
Colonel CConnel,^ and Mr. Howden.* The consideration 
of the data Hhvia obtained has suggested various formulse 
for calculating the discharge due to a given area, but the 
information bb to the amount of flood water said to have 
been discharged from different districts of countiy is so 
discordant, that it seems to me to be impoBEuble witii 
elements so variable to found any formula that can be 
generally useiuh 

The quantity pasedng off during high floods is vari- 
ously stated by diflerent authorities from 1 foot to 30 
cubic feet per minute per acre according to the district 
in which the observations were made.' But the highest 
gauging I have ever got was 15 cubic feet per acre from a 
town district of 630 acres, after three days of nearly con- 
tinuous rain&lh Thunderstorms discharge a very much 
greater amotmt during their short duration. It is stated 
that in August 1846, during a tinmderstorm, 3*3 inches 
fell in 2 hours and 20 minutes, being 85 cubic feet per 
minute per acre.* 

Perhaps the only general result to be gathered from 

> MimiUM of Proeefdingt o/ iHs&atUtm qf Otinl SngUteen, toL xxtIL p. 204. 

* Ibid. p. 21S. 

* Ibid. Td. xxi. p. 84. "ERmfall vtA Grftpontion," by A. Lcmlie, C.B., 
TVoM. Soj/al ScoL 8oc ufArU, toL Tiii 

* ParKmineiitary B«port od HeUopolitao Hun Dnusftge, 1SS8. 



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114 ISLAND NAVIGATION. 

the published observations relative to floods, is tliat 
t?ie flood discharge has a higher ratio to the ordinary dis- 
charge in small than in large rijiers. This is due veiy 
much to the &ct that in a small river a rain-&ll afiects 
every one of its feeders, whereas in a larger river the 
influence of the rain is limited to one portion of the 
district only. If, for example, such a river as the Missis- 
sippi were subjected to an increase of its bulk similar to 
that of small rivers, the countiy through which it flows 
would be entirely devastated. The safety of such a 
country is due to the important &ct that excessive fidls 
of rain, like hurricanes of wind, while at the height of 
their fury are not wide spread, but act on a compara- 
tively lunited portion of the earth's surface. 

Though we cannot, therefore, deduce fi^m data so 
arbitrary any law appHcable to rivers in all districts, we 
are not precluded from dealing with the different sizes of 
floods dischaiged from any particular district ; and as it is 
sometimes desirable to ascertain by gauging the average 
summer flow of a stream, I give the following mode of 
computing the discharge, exclusive of floods, which has 
Mr. Lwiia's bccn proposed by Mr. Leslie.' " First, the gaugings are 
gtnging average all to bo sct down in a table in the order of their quan- 
exoiQdTCof titles, b^^inning at the smallest and going on to the 
""^ largest, or vice versa. The whole number of observations 

is then to be divided as nearly aa possible into four 
equal parts ; whereof the lowest fourth is held to com- 
prehend the extreme droughts, and the highest the floods, 

I mnalet of Procetdmgi of /iwftfultOR ij/ Civil Engmetrt, toL x. p. 327. 



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UNDER-CURREKTS. 115 

The avera^ of the middle half is to be ascertained, and 
all above Uiat quantity is held to be flood-water. 

" A new table ifl then to be constructed, in which all 
the gaugings not exceeding the average of the middle 
half are put down at their actual quantity ; but all above 
the average are put down as equal to tbat average quan- 
tity. The average of the whole of the new table is to be 
considered aa being a fiur estimate of the water flowing id 
the stream, exclusive offloads." 

Under Currents. 

I must offer the further caution, that those rules, Betnitc of roi^ 
firom which the mean Telocity is deduced, on the assump- ^htre imd«r- 
tion that it bears a constant ratio to the surfece velocity, ™'""'' " 
do not apply in many situations which are within the in- 
fluence of the tide. In surveying the Dee at Aberdeen 
in 1812, for example, Mr. Robert Stevenson found that, 
while there was an outimrd upper current of fresh water, 
there was an intoard undeivcurrent of salt water ; so that, 
although the upper stratum was constantiy running to- 
wards the sea, there was a regular rise and fell of the 
surface, produced by the influx of the tidal waters below. 
Another instance of such an under^mrrent, though not 
occasioned by the presence of a river, was found to esdst 
in a marked degree at the Cromarty Firth, where Mr. 
Alan Stevenson, in 1837, found currents greatiy exceed- 
ing the surfece velocity. 

It ie essential in some inquiries to ascertain to what in»tnim«mt« for 

ucertaiulng 

depth the cnrr^its penetiate, and whether under-currents uDder-cnirenu. 
exhibit the same phenomena in regard to direction and 



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116 INLAND NATIOATION. 

velocity as those of the sur&ce ; and aa these inquiries are 
interesting and important, and have lately been much 
discussed in connexion with deep-sea researches, they are 
worthy of detailed notice. 

For small depths the tachometer of Woltmann, whidi 
has been already described, is a convenient and accurate 
instrument for measuring under-currents. I never used 
it myself for depths exceeding a few feet, but I imdOT- 
Btood fixnn Professor Gordon that it has been employed m 
Germany for measuring velocitJee at great depth, by using 
an apparatus erected on a platform, supported on two 
boats, and that Baucourt used it to measure the vdocity 
of the Neva at St. Petersbui^, at depths of 60 feet ; 
Defontune the Rhine, at upwards of 40 feet ; and Funk 
many rivers, at depths of from 40 to 60 feet. But as its 
application under such circumstances may be regarded 
rather as a purely scientific than as an engineering ex- 
periment, it is not necessary to describe it in iim place. 
The direction of the under-currents, which it is sometimes 
interesting to know, cannot, however, be obtsdned by 
means of the tachometer, and I shall describe the plan for 
obtaining an approximation to both the velocity and 
direction of under-currents, which was devised and used, 
I believe, for tiie first time, at the Cromarty Firth, in 
1837, by the late Mr. AJan Stevenson, when he detected 
iJie tidal anomalies already alluded to. It may be well 
to explain t^t the waters of the Cromarty Firth pass to 
and from the sea through the narrow goi^e between the 
Suters of Cromarty, where the width is about 4500 feet, 
and the depth about 150 feet. The mean velocity due to 



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UNDEB-CUBBGNIS. 117 

the column of water passing this gorge, as deduced tcom 
the observed sur&ce velocity, was not suffiaent to ac- 
coimt for the quantity of water actually passed during 
each tide, as determined hy measuring the cubical capacity 
of the basin of the firth. This led to the obeervation of 
the imder-currents through the gorge l^ means of sub- 
merged floats, and it was found that during flood-tides 
the Bur&ce velocity was 1'8 mile per hour ; while at the 
depth of 50 feet the velocity was not less than 4 miles 
per hour, being an increase of 2'2 miles per hour. During 
ebb-tide the sur&ce velocity was 2*7 miles per hour, and 
at 50 feet it was not less than 4'5 miles per hour, b^ng 
aa incroEtse of 1 *8 mile per hour. The instrument by UDdw-eomnt 
which these velocities were measured consisted, as shown crMautrHitb. 
in figure 16, at letter a, of a flat plate of aheetr-iron. 




measuring 12 by 18 inches, having a vane made of the 
same mateoial, and measuring 4 feet in length, fixed at 
right angles to the centre of itw The lower edges of 
tixe plate and vane were loaded with bars of iron, for 
the purpose of causing the instrument to sink to the 
requisite depUi; and it was so slung by the cords 



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INLAND NAVIGATION. 



suspending it aa to preserve the sur&ce of tlie plate in a 
vertical plane. This apparatus was secured by a cord of 
sufficient length to sink it to the required depth, and the 
whole was attached to a tin buoy, letter b, which floated 
on iiie BUt&ce, its form being such as to produce little 
resistance to its passage through the water. The buoy 
served not only to preserve the vane plate at the same 
depth, but aJso indicated its progress through the water 
in a very satis&ctory and often interesting manner. 

The plate, sunk at the depth of 50 feet, when acted 
upon by the force of a strong imder-current, was hurried 
along, carrying Uie buoy, which floated on the sur&ce, 
along with it, as shown by the buoy passing the floats 
thrown out on the water as gauges of the velocity of 
the upper current, one of which is shown at c. The 
only precaution to be observed in making such observa- 
tions, is to exclude that part of the commencement of the 
buoy's course, which is more rapid than it ought to be, 
owing to the effort made by it to overtake the plate, 
which, being sunk first, has been influenced by the velo- 
city of the under-cuirent before the buoy has been 
launched. It is evident that, by means of this simple 
apparatus, we can approximate to the direction as well as 
to the velocity of under-currents ; but it must be kept 
in view tiiat there are several deranging influences in 
operation, which tend to render the results obtained 
merdy approximations to the truth. 

Since I first described these Cromarty Firth obser- 
vations in 1842, many efibrte have been made to ascertain 
tlie existence and strength of under-currenta. 



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UNDBR-CUREBNTS. 119 

Meeara. Carpenter and Jefi&ejs, in 1870, when engaged Under-carrait 
m their deep-sea researches in the " Poreupme survey- deep-s™ 
ing ship, endeavoiired to ascertain the state of the under- 
currents at the Straits of Gibraltar.' The apparatus 
adopted by them for this purpose was arranged by Cap- 
tain Calver, and was identical tn principle with that em- 
ployed at the Cromarty Firth ; the only difference being 
that the under-current float was composed of a basket, 
with pieces of sail-cloth fixed to it, and so disposed as to 
catch the current. The float was weighted with lead, 
and the cord by which it waa suspended, instead of being 
attached to a float as at the Cromarty Firth, was fixed to - 
a boat, the drifting of which indicated the force and 
direction of the under-current. It does not appear that 
more than one or two observations were made with this 
instrument. 

Capt^n Spratt, who has made several observations under-cmrBnt 
on the under- currents of the Sea of Marmora and the^JJJ^^^i^ 
Dardanelles, ui a paper on the under-current theory of 
the ocean, in the Proceedings of tiie Royal Society^ states 
the following as the plan he adopted: — "I never at- 
tempted such ezperimentB by the use of any bulky object, 
such as a boat that ofiered great resistance to the sur&ce 
current. I felt too that a fixed object, as a point of refer- 
ence, was always necessary, such as a buoy or float 
attached to a sinker actually on the bottom. Such 
observations for testing ocean currents should only be 
made in connexion with a fixed object attached to the 

> Report on Deep-tea Retearehei, in July, August, and September 1S7U( by 
W. B. Cupenter, M.D., F.B.S,, »nd J, Owyn JeffreyB, F.E.S. 
' Procadinst qfthe Royal SodUv, 1871, p. 628, 



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120 INLAND NATIGATION. 

bottom, whether in 2000 or 20 fethoms." The float 
which Captain Spratt, after experience, found to answer 
best, was one of thin copper or block-tin, suflpended Uke 
a kite, his observations being in this respect the same as 
those at the Cromarty Firth, while the boat which was 
moored at the Cromarty Firth, in order to obtain the 
relative speeds of the surfitce and under current floats, 
fulfilled the object of his buoy moored with a sinker. 
tJwiBr-ciirHint Jlr. HeniT Mitchell, of the United States Coast 

Boats used by 

Mr.MitcheU. Suivey, describes an inslxument used by him for that 
purpose. It consisted of a tin cylinder, a few inches in 
diameter, and long enough to reach from the surface 
nearly to the bottom. Tubes 40 feet in length were 
used for this purpose. They were 3 inches in diameter, 
made in separate sections, ^-tight, but with stop-cocks 
for letting in water, that they might be practically filled, 
so as to sink to the proper depth. As the tube drifted 
nearly upright in the water, with its top protruding a 
few inches above the surface, its velocity indicated the 
mean motion of the stream. If it leant backwards or 
forwards, it showed that its foot rested on a stratum tJiat 
had greater or less motion than the sur&ce drift ; and 
if its angle of direction diflered from that of ihe surface 
log, iiie action of an under-current was recognised, whose 
course was at variance with that of the sur&ce drift. 

Mr. Mitchell also says, that very good " results have 
been obtiuned by using two hollow copper globes of 2 feet 
diameter each, connected by ^ inch wire rope. The sink- 
ing globe is filled with water, but the other is loaded only 
enough to sink nearly to its pole. The upper globe has 



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UNDER-CURRENT8. 121 

a long line secured to it, aod its motion is recorded at 
the same time that an observation is made with the 
sur&ce Ic^, like the compoimd float iised by Dr. Anderson 
at the Tay, aa described at page 99. 

Mr. Mitchell says, "Let us Buppose that the two 
globes present equal effective areas (great circles) to the . 
drifts in which they swim, then iheii velocity will be a 
true mean of the rates of the sur&ce and imder currents ; 
».e. J(a;+y) where x and y represent respectively these 
rates. The velodty of the imder-current may therefore 
be found by subtracting the surtee rate from twice that 
of the connected globes." 

This formula no doubt gives the mean for the veloci- 
ties of the two strata in which the balls are floating, and 
it would give the mean for the whole column of water, 
provided there is a regular gradation between these two 
observed velocities, but it does not provide for any in- 
equality of velofaty, or for any anomalous velodty, such 
as has been stated to exist at the Dee and the Cromarty 
Firth. This objection might perhaps to some extent be 
removed if it were practicable to suspend balls similar to 
those used by Mr. Mitchell, at short intervals on tits 
wire rope. But for engineering purposes, the object of 
ascOTtaining the undercurrents has, in my experience, 
alwa^ been to calculate the discharge ; and it is obvious 
that for this purpose we must determine the thickness 
of the different strata moving at difierent velocities, so 
as to ascertain the different sectional areas to which ihe 
YtAodiieB &pply> and this not at one but at several points 
on Uie cross section of the channel or passage through 



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122 INLAND NAVIGATION. 

which the current waa flowmg. Until we have some 
method of ascertaining the velocities at different depths, 
and the sectional areas corresponding to these velocities, 
it is not possible to arrive at the discharge, and all obser- 
vation on the strength and duration of under-currenta 
must be regarded by the en^^neer, in making calculations, 
to be simply approximate. 

The remarkable under-currents of the Cromarty Firth 
are mainly, if not altogether, due, I believe, to the con- 
figuration of the bottom, and the circumstances under 
which the tidal wave approaches and recedes from the 
shore. A powerful oceanic under-current during flood- 
tide- in a stoitum of water of high specific gravity and low 
temperature, setting dead along the coast, would natur- 
ally creep along the rising bottom of the sea, and flow 
into the deep inlet of the firth, mingling imperfectly with 
the surrounding water, maintaining its character of a dis- 
tinct stream, and increasing the under-velocity of the 
flood-tide; and if we suppose a similar rapid counter- 
current to sweep along the coast at ebb-tide, its ten- 
dency would be to draw off the lower stratum of denser 
and colder water, and thus to increase the velocity at 
or near the bottom during ebb-tides. Of the ezistence 
of such distinct ocean currents, some at great depths, 
and others superficial, m^taining their character, and 
mingling slowly with the surrounding ocean, there are 
many striking examples ; among others, the aur&ce- 
current of the Gulf Stream, which, flowing from the 
Gulf of Mexico, skirts the coast of the United States, 
and can be traced as a distinct body of water by its 



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UKDER-OURRBNTS. 123 

difference of temperature as &r as the banliB of New- 
foundland. In the month of July I found the tempera- 
ture of the sea, as tested at various pointa between the 
shore of America and the edge of the Qulf Stream, to 
average 60° FaL ; while in lat. 41° N., long. 61° 52' w., 
the vessel being in the track of tbe Crulf Stream, the 
temperature of the water was 70°. After leaving the 
influence of the Gulf Stream, the temperature within 
a few hours' sail fell to 60°, whidi was the average of 
the observations made during the remainder of the voy- 
age to the English Channel, ascertained as accurately as 
the &cilities granted to a passenger by a packet-ship 
permitted. 

The cause of ocean currents is obscure. They nocwueot 

■ « 1 ■ 111 undsr-ottcrmta, 

doubt are occasionaUy caused or increased by gales of 
wind. But, as I pointed out in the first edition of this 
book, no current can be generated without a difference of 
head, which again may be produced either by a difference 
of level in water of the same density, or by a difference 
of specific gravity in columns of water of the same height.. 
The examples I have given of the di&rences of levels 
^dating in rivers and estuaries at certain states of the 
tide, affijrd Bu£B.cient proof of the existence of currents 
fiwm that cause. It is not unusual to employ the ex- 
pression indraught, to describe the fiow of water into a 
bay or creek, and to hear it used so as almost to imply 
the existence of some inherent attraction in the bay or 
creek for the watw which flows into it. But the flow of 
water in all such cases is caused by the pressure due to 
difference of level or density, or both combined ; and when 



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124 INLAin) NAVlQATrON'. 

the bay or creek geta filled up, and its sur&ce attains 
a mifficient height to balance the pressure of the source 
of its supply, or the momentum of the moving column of 
water where converging shores cause the level of the 
water to rise, the indrau^t disappears. 

Dbnsitt of Salt and Fresh Watee. 
Before leaving this part of the subject, however, I must 
say something more as to the separation of the under 
from the swperjicial strata of water, and explain that 
other species of disturbance which is due to the different 
density of salt and fi-esh water. 
HBtbod»for The first observations on this subject to which I shall 

«podin«v at refer were those made by my fether on the river Dee, 
diOsKiit depths, in Aberdeenshire, in the summer of the year 1812, 
when engaged m surveying that river in r^erenoe to a 
salmon-fishing case.^ " He observed in the course of his 
surv^ that the current of the river continued to flow 
towards the sea with as much apparent velodty dutii^ 
flood as during ebb tide, while the sur&ce of the river 
rose and fell in a regular manner with the waters of the 
ocean. He was led firom these observations to inquire 
more particularly into this phenomenon, and be accord- 
ingly had an apparatus prepared, under his directions, at 
Aberdeen, which, in the most satis&ctory manner, showed 
t^e existence of two distinct layers or strata of water ; 
the lower stratum consisting of salt or sea water, and the 

' Report to the Earl of Abeidean aod the other Pniprieton of the " R>iL " 
and " Stell " Fiahing* of tlie Hirer Dee, kt Aberdeen, by Robert SteTeneon, 
Civil Engineer, Edinburgh, Feb. 1813 ; aod SteTemon'i Beii-Rodt LigktJtoute, 
p.7«. 



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DENSITY OF SALT AND FUESH WATER. 123 

upper one of the fresh water of the river, which, from its 
specific gravity b^ng lees, floated on the top during the 
whole of flood aa well as ebb tide. The apparatus con- 
sisted of a bottle or glass jar, the mouth of which mea- 
sured about 2^ inches in diameter, and was carefully 
stopped with a wooden plug, and luted with wax ; a hole, 
about half an inch in diameter, was then bored ui the 
plug, and to this an iron p^ was fitted. To prevent 
accident in the event of the jar touching the bottom, it 
was coated with flannel The jar so prepared was fixed 
to a spar of timber, which was graduated to feet and 
inches, for the conveniency of readUy ascertainii^ the 
depths to which the instrument was plunged, and from 
which the water was brought up, A smaJl cord was at- 
tached to the iron pin for tiie purpose of drawing it at 
pleasure for ^e admission of the water. When an experi- 
ment was made, the botUe was plunged into the water ; 
by drawing the cord at any depth within the range of the 
rod to which it was attached, the iron peg was lifted or 
drawn, and the bottle was by iim means filled with 
water. The p^ was again dropped into its place, and 
the apparatus raised to the sur&ce, containing a specimen 
of water, of the quality at the depth to which it was 
plunged. In this manner the reporter ascertfuned that 
the salt, or tidal water of the ocean, flowed up the chan- 
nel of the river Dee, and also up Footdee and Torrybum, 
in a distinct stratum next the bottom and under the 
firesh water of tJne river, which, owing to the specific 
gravity being less, floated upon it, continuing perfectly 
fi^sh, and flowing in its usual ooiuse towards ihe sea, the 



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126 INLAND NATIOATION. 

only change discoverable being in ite level, which was 
raised by the salt water forcing its way under it. The 
tidal water so forced up continued salt, and when the 
specific gravities of specimens from the bottom, obtained 
in the maimer described, were tried, and compared with 
those taken at the sur&ce, by means of the common 
hydrometer of the brewer (the only instrument to which 
the reporter had access at the time), the lower stratimi, 
when compared with that at the surfitoe, was always foimd 
to possess the greater d^ree of specific gravity due to salt 
over fresh water." 

The instruments now used for obtaining water frxim 
difierent depths are more perfect in their construction 
than the original instrument used for that purpose at the 
Dee, which was made for a temporary purpose. Various 
constructions have more recently -been tried for experi- 
menting on this subject, by Scores!^, Sabine, Dr. Marcet, 
and others, but for ordinary engineering inquiries I can 
confidently recommend the instruments I am about to 
describe, which I have termed hydrophoree, and have 
extensively employed in engineerir^ surveys. 

Fig. 17 represents a hydrophore used for procuring 
specimens of water from moderate depths, drawn on a 
scale of one-tenth of the full size. It consists of a tight 
tin cylinder, letter a, having a conical valve in its top, h, 
which is represented la the diagram aa being raised for 
the admission of water. The valve is fixed dead, or im- 
moveable, on a rod working in guides, the one resting 
between two uprights of brass above the cylinder, and the 
other in its interior, as shown in faintly dotted lines. 



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DENSITY OF SiLT AND FRESH WATER. 127 

The Talve-rod is hy this means caused to move in a truly 
vertical line, and the valve attached to it consequently 
fills or closes the hole -in the top of the 
cylinder with greater accuracy than if 
its motion was undirected. A graduated 
pole or rod of iron, c, which in the dia- 
gram is shown hroken off, is attadied to 
the instrument, its end heing inserted 
into the small tin cylinder at the side of 
the large valve or water cylinder, and 
there fixed by the damp screws shown „ 
in the diagram; the bottom of the water 
cylinder may be loaded with lead to any 
ertent required, for the purpcffle of caus- 
ing the apparatus to sink; but this, 
when an iron rod is used for lowering it, is hardly neces- 
sary. The spindle carrying the valve has an eye in its 
upper extremity, to which a cord is attached for the pur- 
pose of opening the valve when tiie water is to be ad- 
mitted, and on releaong the cord, it again doses by its 
own weight. When the hydrophore is to be used, it is 
lowered to the required depth by the pole which is fixed 
to its fflde, or if the depth be greater than the range of 
the pole, it is loaded with weights and let down by means 
of a rope so attached as to keep it in a vertical position. 
Care must be taken, while lowering or rai^ng it, that the 
small cord by which the valve is opened be allowed to 
hang perfectly free and slack. When the apparatus has 
been lowei«d as fiu* as is required, the small cord is 
pulled, and the vessel is immediately filled with the water 



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128 INLAND NAVIGATION. 

which is to be found at that deptii. The cord being then 
thrown slack, the valve descends and closes the opening, 
and the instrument is slowly raised to t^e sur&ce by 
means of the rod or rope, as the case may be, care being 
taken to preserve it in a vertical position. This appa- 
ratus is only applicable to limited depths, but will gene- 
rally be found to answer all the purposes of the civil 
engineer. 

The form of hydrophore represented in fig. 18 is xised 
in deep water, to which the small one just described is 
inapplicable. It consists of an egg-shaped 
vessel, letter a, made of thick lead, to give Uie 
apparatus weight, having two valves, b and c, ■ 
one in the top and anoiiier in the bottom, both 
opening upwards ; these valves (which are re- 
presented as open in the diagram) are, to insure 
more perfect fitting, fixed on separate spindles, 
which work in guides, in the same manner as in 
.the instrument shown in fig. 17. The valves, 
however, in the instrument I am now describing, 
are not opened by means of a cord, but by the 
Fro. 18. impact of the projecting part d, of the lower 
spindle on the bottom, when the hydrophore is sunk to 
that depth. By this means the lower valve is forced 
upwards, and the upper spindle (the lower extremity of 
which is made nearly to touch the upper extremity of the 
lower one, when the valves are shut) is at tbe same time 
forced up, carrying along with it the upper valve which 
allows the air to escape, and the water rushing in fills the 
vessel On raising the instrument from the bottom both 



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DENBTTY OF SALT AND FRESH WATER. 129 

valves again shut by their own weight and that of the 
mass of lead d, which forma part of the lower spindle. 
The mode of using this hydrophore is sufBciently obvious ; 
it is lowered by means of a rope, made &at to a ring at 
the top, as is shown in £g. 18, until it strikes on the 
bottom, when the valves are opened in the manner 
described, and the vessel is filled ; on raising it the valves 
close, and the vessel can be drawn to the surface without 
its contents being mixed with the superincumbent water 
through which it has to pass. This iDStrument weighs 
about half a hundredweight, and has beoi easily used in 
fi-om 80 to iO &tiiom8 water in making raigineering 
surveys, and could no doubt, if necessary, be employed 
for much greater depUia It is represented in the cut on 
a scale of one-twraitieth of the full size. 

The hydrophore employed by the Scientific Ezplora- H;dropiion 
tion of the Deep Sea, m 1870, was suggested by the (opiontiom, 
hydrogr£^her to the Admiralty, and consisted of a strong 
cylinder of brass, 26 inches long and 2*3 inches diameter, 
holding about 60 oz, of water in the disk which closes it ; 
at each end there is a circular aperttu^, into which a 
conical valve is accurately fitted. "While this bottle is . 
descffliding through the water with the sounding appar- 
atus the valves readily yield to the upward pressure, and 
a continuous current streams through it, but so soon as 
the descent is checked, either by the arrival of the appar- 
atus at the bottom, or by a stop put on the lines from 
above, the valves fell into their places, and there enclose 
the water that may fill the bottle at the moment. The 
working of this simple apparatus was foimd to be entirely 



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130 INLAND NAVIGATION. 

satia&ctoiy. It is obvious however thai the deep-water 
hjdiophore would not be found so useful for the smaller 
depths requisite in engineering surveys as the two forms 
of the instrument which I have described and used since 
1842.^ 

Dr. Marcet, in a paper on the specific gravity of sea- 
water, in the Philosophical Transactions for 1 8 1 9 , desmbes 
an instrument he used for obtaining water from the 
bottom, consisting of a cylindrical vessel with an ap^ure 
at either end fitted with valves opening upwards. These 
valves when closed were secured by springs, but were so 
made as to be kept open by a weight acting on the springs, 
and suspended below the vessel When this weight 
touched the bottom the springs were relieved, and closed 
the valves, which .remained shut, and enclosed the sped- 
men of water. I do not think however that this arrange- 
moit is BO simple as that shown in the preceding figure, 
which, as used in moderate depths, I never found to &iL 

In all these experiments, the water being emptied 
into bottles, is corked up, sealed, and labelled with 
certain ninnbers, which should be entered in a book con- 
taining remarks as to the place of observation, time of 
tide, and such other particulars as, from the nature of tiie 
inquiry, seem to deserve notice, and the water thus pre- 
served may be subjected to analysis. 
f The appearance of fresh or brackish water floating on 

the sur&ce of the sea, as described at the Dee at Aber- 
deen, is no doubt fiinuliar to most observers. It occurs 

1 Frelinuiuvy Report of the Scieatifia Exploration of tlie Deep Se«, by Dr. 
Carpenter, J. Owyn Jeffireyt, F.B.3., and Wyrille TtamnMn, LUD., ISTOi 



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DENaiTY OF SALT AXD YRBSU WATER. 131 

indeed more or less at the mouths of all rivers, being most 
apparent when they are in flood, &om thf> browner tinge 
given to the water, which ia sometimes discoloured many 
nules at sea. Father Manuel Bodriguez, a Spanish 
Jesuit, speaking of the Amazon, says' — " This river is like 
a tree ; its roots enter &r into the sea, as into the land. 
It communicates to it a flavour, so liiai at 80 leagues 
within the sea its waters are seen, and taste sweet, and 
in a semicircle of 100 leagues in circumference they form 
a gulf not the least degree brackish, so that sailors call it 
the treek sea," — a statement which mig^t almost seem 
incredible, had not Sir Edward Sabine, in 1827, found 
something which goes flu- to bear out the correctness of 
the Spaniard's account, and which he describes in the 
following words : — "At 10 A.M. on the 10th of Septem- 
ber, whilst proceeding in the full strength of the current, 
exceeding, as already noticed, 4 knots an hour, a sudden 
and very great discoloration in the sur&ce-water ahead 
was reported &om the mast-head, and irom the very 
rapid progress which the ship was making was almost 
immediately afterwaids visible from the deck. Her posi- 
tion in 5° 08' north latitude, and 50° 28' west longitude, 
sufficiently apprised us that the discoloured water which 
we were approachiug could be no other than the stream 
of the river Amazon, preserving its original impulse at a 
distance of not less than 300 miles from the mouth of the 
river, and its waters being not yet wholly mingled with 
those of the ocean of greater specific gravity, over the 
sur&ce of whic^ it had pursued its couise, 

Madrid, 1S84, p. 18. 



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182 INLAND NAVIGATION. 

" We had just time to secure Bome of the blue water 
of the ocean for subsequent ezamiiiation and to ascertain 
its temperature before we crossed the line of its separa- 
tion from the river-water, the division being as distinctlj 
preserved as if they had been different fluids. 

" The direction of the line of separation was n.w. by 
N., rather northerly ; great numbers of gelatinous manne 
animalB, species of the genus Physalia, were floating on 
the edge of the river-water, and many birds were fishing 
apparently on both sides of the boundary."' 

I have occasionally seen these brownish-coloured 
patches at a considerable distance from the coast, and on 
one occasion, in the Pentland Firth, on drawing a bucket 
of this brownish water, and comparing it with that of the 
sea after passing through the patch, it was found to be 
distinctly brackish. It is well known to the crews of 
"welled" smacks employed in cod-fishing on our coasts 
that they invariably lose a portion of their live stock if 
they happen to encoimt«r what they term a "fresh," 
which is believed by them to be a brackish portion of 
t^e sea, caused, no doubt, by the imperfect mixture of 
the fi:esh water discharged from rivers. 

In subjecting waters for examination to ascertain the 
proportion of fresh and sea water, two methods may 
be adopted — ^first, by taking their specific gravity; or 
secondly, by evaporating a certain quantity, and ascer- 
tfuning the amount of saline matter left. The result may, 
in either case, be to some extent affected by the quantity 
of v^etable matter in suspension, but it is sufficiently 

' PkUotoplneal Magaxint, toI, IxviL 



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DENSITY OP SALT AND FRESH WATER. 133 

aoourate for most engineering inqimiea The specifio 
gravity test is the most convenient, and that which 
is generallj adopted, the specific gravity being taken 
with an ordinary hydrometer; the standard employed 
is distilled water when at the temperature of 62° Fah- 
renheit as 1000. Dr. Marcet says that in general the 
waters of the ocean, whether taken from the bottom or 
the sur&ce, contain most salt in places where the sea is 
deepest and most removed from land, and in his tables of 
experiments he gives the specific gravity of some ocean 
samples as high as 1030*9. From various observations, 
made at difierent parts of oiu* coasts, I am disposed to 
state the specific gravity in these localities at 1026. I 
have found that in any experiments made in our rivers 
and estiiaries the densities varied from 1000 to 1026, 
aad occasionally during flood-tide the difierence in specific 
gravity between the surfiuse and bottom is veiy striJdng, 
as pointed out in Mr. Stevenson's experiments of 1812 at 
Aberdeen. 



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CHAPTER VI. 

THE " RIVER PROPER " COMPAEIMENT. 

Sizes of riven proportioDsl to the extent of country djuoed— The UiHiiiBippi an 
flx«m^ of ft Urge river — BeaoriptioD of !ta luvjg&tion, current!, knd dU- 
chargo— Worlu propawd for its improvemeDt — Means nsed for readering the 
nppe'r portioni of snull riren navigable, by stancheB, dams, and lochi — Im- 
provementi of npper poitionB of ContiDciLtal riven, aach M the Rhine and 
Danabe. 

In following out the division of the subject propoBed 
at the conclusion of Chapter IIX, 1 have, in treating of 
rivers, to consider in tJie first place what has been termed 
the upper or " river proper " compartment. And as re- 
gards the use made of such streams for the purposes of 
navigation, or the works calling for the oi^neer's asEOst- 
ance to render them navigable, there is not much to refer 
to in this country. The magnitude of a river and its use- 
fulness for navigation may be scud, under certain condi- 
tions, to be proportional to the extent of country which is 
drained. Thus in continents we find rivers of great 
magnitude, fed by the drainage of vast tracts of surround- 
ing land, rolling their contents in a broad, deep current 
to the ocean, and affording a highway for vessels of the 
largest class to pursue their course for hundreds of nules 
into the interior of the countiy. Of such is die Mississippi, 
which maintains, for a distance of nearly 1200 miles 
above New Orleans, an average Weadth of 3300 feet, and 
a depth of 115 feet. The Ohio, which joins it at this 



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THE "EIVBE proper" COMPARTMENT. 135 

place, is navigable to Fittaburgh, where I have seen from 
tMrty to forty laige-sized steamers lying at the quays of 
that truly inland port> which were all engaged in trading 
to New Orleans, on the Gulf of Mexico/ being a river- 
navigation of upwards of 2000 miles. 

In considering the improvement or maintenance of 
such a navigation as this, the engineer has to deal chiefly 
with the control of the enormous body of water which it 
dischaigeB. His difficulty does not consist in deficient 
depth or breadth of navigable channel, but in the magni- 
tude of the floods with which he has to conteaid, and the 
provision he has to make for retaining thran wiUiin such 
limits as to secure t^e safety of the surrounding district. 

In less extended tracts of country than the valley of 
the Missisfflppi, the rivers are proportionally smaller ; and 
when we come to consider our own island, we find that its 
area and dnunage are only sufScient to supply steeams of 
the smaller clas& 

The MiBsissnTJ. 

The MisEossippi is the most gigantic river-navigation 
in the world, and some &cts as to its navigation, taken 
from iJbe elaborate report of Mr. Charles EUet,' which was 
made to the Government of the United States, cannot £ul 
to interest the en^neer, and will not, I am sure, be con- 
sidered out of place in this work ; for, altiiough they can- 
not be sfud to apply to British, or even Continental rivers, 
th^ will at least beet serve to show by comparison the 
smallness of our own rivers when I come to speak of them. 

^ Sketch qf OMl Biti;intai7ig of North America, b^ D»Tid SteTenMm, C.E. 
* The MU^fippi OMd Ohio Sivert, b; Chule* EUet, Philkdelphu, 1853. 



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136 INLAND NAVIGATION. 

It appears, from the mfcamation given in Mr. EUet's 
work, that the Mississippi varies from 2200 to 5000 feet 
in width, the average width being assumed as 3300 
feet. It is from 70 to 180 feet in depth, the average 
being 115 feet. The area of the cross section varies from 
105,544 square feet to 268,646 square feet, the average 
being 200,000 square feet. The length, from its junction 
with the Ohio to the Gu]f of Mexico, is 1178 miles, 
and its average &U at full water is 3^ inches per mile, 
and in absence of floods (or during summer and autumn) 
%^ inches per mile. 'Die length of the Ohio, from its 
junction with the Mississippi to Pittsburgh {the head of 
the navigation for laige vessels), is 975 miles, and the 
average inclination is about 5^ inches per mile. From 
Pittsburgh to Olean Point, the head of tiie navigation for 
small vessels, the distance is 250 miles, and the inclina- 
tion 2 feet 10 inches per nule. When the water is high, 
even steamboats have ascended to Olean Point, which is 
2400 miles frx»m the Gulf of Mexico ; and in doing so, 
have had to overcome a current which at some places 
runs with a velocity of 5 miles per hour. Generally 
speaking, vessels have no difl^nilty, in the lower or more 
open part of the stream, iu avoiding the streng^ of the 
currents by keeping in-shore. But in the Ohio much in- 
convenience is felt during dry seasons frum the currents 
at certain parts of the river ; and I have seen a steamer 
unable to overcome ihem until assisted by a warp attached 
to an anchor dropped ahead of the vessel, in the middle 
of the chMmel, by which, after considerable detention, she 
was "warped through the rapid;" there are no such 



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THE "EIVER PROPEB COMPABTMElfT. 137 

^oals, however, in tlie Misaissippi, nor indeed below 
LouisTille on the Ohio. The dischai^ of the Mississippi 
ia computed by Mr. Ellet, at high water, at 1,280,000 
cubic feet p^ second ; and its drainage he estimates at 
1,226,600 square miles. When the auttmmal rains set 
in, the river rises above its summer level to the enormous 
extent of about 40 feet at the mouth of the Ohio, and 20 
feet at New Orleana In investigating the phyacal char- 
acteristics c^ this mighty stream, Mr. EUet found — 1st, 
That the average sur&ce velocity in the centre of the 
river was 5 miles per hour, and occasionally the speed 
reached 7 miles per hotu" ; 2d, By using under-durent 
floats, he found iJiat the speed of a float, supporting a 
line of 50 feet long, was always greater than that of the 
surfiice float — the avOTage increase of velocity being 2 per 
cent. ; 3d, The results of the experiments made lead him 
to conclude that the mean velocity of the Mississippi is 
about 2 per cent, greater than the mean sur&ce velocity ; 
ith, In coming to this conclusion, no account is taken of 
such observations as show remarkable imder-currents, the 
velocity of which were in some places found to be 17 per 
cent, and 20^ per cent, greater than tlie sur&ce velocities ; 
5th, While the mass of water which the channel of the 
Mississippi bears is running downwards with a central 
velocity, the current next the Elhore is sometimes fo^ind 
to be running upwards, or Id the opposite direction, at 
the rate of 1 to 2 miles per hour ; 6th, While the water 
is running downwards in the one side of the river, it is 
often found with an appreciable slope, and visible current 
running upwards on the other side of the river ; 7th, The 



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138 INLAND NAVIGATION. 

suT&ce of the river is therefore not a plane, but a pecu- 
liarly complicated warped surfece, varying from point to 
point, and inclining alternately from side to side. After 
considering all the conflicting results derived frvjm his 
investigations, Mr. Ellet, in order to obtain the mean 
vdocity and discharge of the river, employed the formula 
as already noticed : — 

M = 0-8 V 

where V = the velocity of central flurface cnrrent in feet per 
second, 
d B maximum depth of river in feet at place of observation, 
/ = elope of surface in feet per mile, 
M = the mean velocity in feet per second, 
a = area of crosa section of river in feet, 
D = di^iharge of river in cubic feet per second. 

In discussing the various formulee for velocities and 
discluu^es, we have already seen, at page 109, that the 
formula applied to the Mississippi by Mr. Ellet does not 
apply to such rivers as the Tay, or to smaller water- 
courses ; and, indeed, until the result which he has given 
has been compared with the discharge obtained by acttml 
measurement of the velocities at different parts of the 
crosb section, we do not think that the discharge of the 
Mississippi, which has be«i calculated by Mr. Ellet, can 
be relied on as accurate. 

The " peculiarly warped " form assumed by the sur- 
&ce from side to side and from point to point of tiie 
water, is an interesting feature, which renders any 



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THE " RIVER-PBOPER " COMPABTMENT. 139 

gauging of tJbe discharge exceedingly difBctiit, and may, 
I think, be accounted for on the " principle of the con- 
servation of forces," which is more fully noticed in the 
chapter on tidal riverB. If we can imagine an upright 
wall opposed as a batrier across the column of water 
moving down the Mississippi, so as to arrest its prepress, 
the surfece of tiie water would not rise equally against 
the fece of the wall or barrier fi:x>m mde to side of the 
river. The rise or elevation of the sur&ce wotiLd be 
highest when Hiq momentum of the water was greatest. 
Thus, &r example, in a bridge the water rises highest on 
the cut-wateis of those piers which stand in the greatest 
depth and strongest current, and so at the Mississippi the 
column of water, though not stopped by a soUd obstruc- 
tion, is nevertheless opposed by numerous contractions, 
abrupt bends, and islands cauaiag the sur&ce to rise un- 
equally, and thus to generate counter or side currents 
and all the disturbance due to unequal pressure which 
Mr. KUet describes. 

The chief object of the investigations made by Mr. 
Ellet was the prevention of floods, which have recently 
increased both in number and extent. This he attributes — 

First, To extended cultivation, by which evaporation 
is supposed to be diminished, the drainage increased, and 
the floods hurried forward more rapidly into the coudtiy 
below. 

Second, To the extension of the embankments along 
the banks of the Mississippi and its tributaries, by which 
water that was formerly allowed to spread is now con- 
fined to the channel of the river. 



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140 INLAND NAVIGATION. 

Third, To what are tenned cut-offe, or straight cute, 
by which the distance is shortened, and the slope and 
velocity increased, so that the water is brought down 
more rapidly from the country abova 

Fourth, To the gradual extension of the delta into the 
sea, so as to lengthen the lower course of the river, to 
diminish the slope and velocity, and thus to throw back 
the water on the land above. 

The works suggested for protectiiig the country 
against floods are — 

First, More sufficient embankments. 

Second, The prevention of further cut-oflfe, or works 
for straightening the upper parte of the tributaries of the 
river. 

Third, The enlargement of the seaward channels or 
outlete. And 

Fourth, The creation of large artificial reservoirs, by 
placing dams across the outlete of the lakes or distpant 
tributaries, so as to compensate for the loss of the natural 
overflow of the water, which is checked by the embank- 
mente for protecting the country in the lower part of the 
rivffl". 

I am not aware whether any of Mx. Ellet's sugges- 
tions have been carried out. 

His report had reference chiefly to the question of 
drfunage, — an important one in a district where the flood- 
waters of tJie river attain an elevation consideraUy higher 
than the adjoining coimtry. Mr. Ellet says that the river 
carries at aU times a vast amount of earthy matter, which 
the current is able to carry fiirward as long as the river is 



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THE " RTVEE-PBOPER " OOMPARTMENT. HI 

confined to its channel ; but when the water overflows its 
confining embankments, it deposits the particles in sus- 
pension on either side, leaving the heavier matter nearest 
to the river ; consequently the borders of the river, which 
receive the first and heaviest deposit, are raised by suc- 
cessive floods above the general level of the delta, and 
ultimately assume a cross section similar to ih&t shown 
in fig. 19, where the horizontal dotted line shows that the 
surfiwje of the river is higher than the level of the land 
on eith^ side. Hx. Ellet ^ves this as an average section, 
obtaloed from a number of surveys made at the lower part 




Vm. 19. 

of the delta, and states that the land is from 1 8 to 20 feet 
lower than the river. 

The Mississippi and its tributaries drain the whole of 
the North American continent, which extends fix)m north 
to south between the Great Northern I^akes . and the 
Gulf of Mexico, and firom east to west between the ranges 
of the Alleghany and Rock Mountains, These fertile 
valleys include nine of the United States of America. 
The geological formation of the country shuts up this 
immense tract of land from any direct coromumcation 
with the seas which wash the eastern and western coasts 
of the continent ; for if we trace upwards in their courses 
of many hundred miles through the eastern States, these 



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142 INLAND NAVIGATION. 

uumerouB large naTigable riverB wluch dischaige into the 
Atlantic, we find them holding the character of streamleta, 
long before we penetrate even to the range of these fertile 
valleyfl ; and on the western coast of the country the 
range of the Rocky Mountains, extending along iiie shores 
of the Pacific, presents an insurmountable barrier to any 
direct water-communication with that ocean. The Missis- 
sippi, however, and its numerous tributaries, aflfoid a 
perfect and easy access to the remotest comer of these 
regions. The source of the river is said to have been 
discovered, in the year 1833, to the westward of the 
Great Lakes, at the distance of about 3000 miles fivm the 
Gulf of Mexico, and at an elevation of about 1500 feet 
above its surface. The river flo-vra fiom ito source as a 
small stream, and gradually gathering strength, passes 
over the falls of St, Anthony, afber which at every stage 
of its course it gains accessions of strength from the 
numerous small rivers that pour in their tributary streams 
irom all directions, untU it is joined by the great Missouri. 
The character of its water, formerly clear and tranquil, is 
here completely changed, and the combined streams of 
two rivers flow on in a deep and muddy current. The 
Ohio, the Arkansas, the Bed Eiver, and many other large 
streams, fell into this g^ant of rivers, which, swelled by 
the waters of its various tributaries, at last pours into 
the Gulf of Mexico.^ The abrogate length of the various 
tributaries of the Misassippi has been computed to be 
upwards of 44,000 milea 

But leaving the class of g^ant rivers, of which the 

' SteTeiiKiii'a American Eagiiuerirtif. 



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THE "RIVER proper" COMPARTMENT. 143 

is a type, and whieh, without the help of Heuutmedror 
artmcial works, anbrd ample width and depth for ex- upper portiona 

111. » . . 1 ,1 . ■. 1 "' Britiih lifers 

tended lines of navigation, we shall consider the means uvigibie. 
used for rendwing the upper portions of the smaller 
class of rivers navigable. 

Telford saya,^ " A river, in its natural current, is more 
or lees deep &om circumstances which need not here be 
described, and its navigation is usually impeded by shal- 
lows and rapids — ^Inconvemencies which the ingenuity of 
man has striven to overcome, ever since his boats became 
too large and too heavy for portage, as is still in use for 
conveyance by canoes in the North American fur-trade. 
The first expedient which occurred was to thrust the boat 
as nearly as possible to tibe rapid, and having well &s- 
tened her there, to awiut an increase of water by rain ; 
and this was sometimes assisted by a collection of boats, 
which, ]yj forming a kind of floating dam, deepened the 
water immediately above, and threw part of the rapid 
behind themselves. This simple expedient was still in 
practice at Sunbury, on the river Thames, since the be- 
ginning of the present century ; and elsewhere the custom 
of building bridges almost always at fords, to accommo- 
date ancient roads of access, as well as to avoid the diffi- 
culty of founding piers in deep water, afforded oppor- 
tunity for improvement in navigating the rapid formed 
by the shallow water or ford ; for a stone bridge may be 
formed into a lock or stoppage of the river by means of 
transverse timb^^ &om pi^ to pier, sustaining a series 
of boards called paddles, opposed to the strength of the 

> TeUord'a L^e, p. 67. 



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144 INLAND NAVIGATION. 

current, as was heretofore seen on the same river Thames, 
where it passes the city of Oxford at Friar Bacon's Bridge, 
on the road to Abingdon. Such paddles are there in 
use to deepen the irregular river channels above that 
bridge ; and the boat, or collected boats, of very consider- 
able tonnage, thus find passage upwards or downwards, 
a single arch being occasionally cleared of its paddles to 
afford free passage through the bridge." 

Sir William Cubitt also says, there were thirteen 
old stanches, as they were called, on the Stour, in Essex, 
These conosted of two substantial posts, which were 
fixed in the bed of the river at a sufficient distance apart 
to permit a boat to pass easdy between them, and con- 
nected at the bottom by a cross cill. TJpon one of these 
posts was a beam turning on a hinge or joint, and long 
enough to span the opening. When the "stajich" was 
used, the boatman turned the beam (which was above 
the level of the water) across the openit^, and placed 
vertically in the stream, a number of narrow planks rest- 
ing against the bottom cill and the swinging beam, thus 
forming a weir which raised the water in the stream about 
5 feet higL The boards were then rapidly withdrawn, 
the swinging beam was turned back, and all the boats 
which had been collected above were carried by the flow 
of water over the shallow below. By repeating this oper- 
ation at given intervals, the boats were enabled to pro- 
ceed a distance of about 23 miles in two or three daya 

This primitive system, which was at one period very 
common in England, has been superseded by throwing 
permanent dams across the river, so as to convert its 



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THE " RIVBE PROPER COMFABTMENT. 145 

channel into a series of deep-water reaches, and the boato 
paas from one reach to the other by means of side-cute 
with locks. This plan, which in America is called " still- 
water navigation," has been extensively carried out on the 
rivers of that country. I saw a good specimen of it on 
the Schuylkill, in Pennsylvania. That river was rendered 
navigable by thirty-four dams constructed in the bed of 
the stream, so as to raise the level of the water and con- 
vert the river into thirty-four reaches of navigable water. 
varying in Iraigth according to the rise in the river's bed. 
The barges pass from the different reaches through a short 
side-cut, in which there is a canal lock of the ordinary 
construction. The navigation is upwards of 100 miles 
in length, and was navigated by boats of about 60 tons 
burden. The same plan has been carried out on a pretty 
lai^ scale by the late Mr. Kendel and Mr. Bearilmore, 
for the improvement of the river Lee, and by Sir "William 
Cubitt on the upper part of the Severn, where the river 
has been divided into four reaches, having a depth of 6 
feet, with side-cuts and locks having a lift of 8 feet each. 

It must be obvious that the works for forming slack- 
water navigation closely resemble the ordinary canal works 
which have been already described, and the side cuts and 
locks for passing vessels from reach to reach of the river 
are identical, and require no Airther notice. 

But the operation of datntifimg up the river is impor- wein 
tant, and cannot be passed over without special notice, 
A river dam is a work in all cases demanding c^:«iul con- 
enderation, not only as regards its safe construction so as 
to resist the foroe of the stream, but also with reference 



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146 INLAND NATIQAnON. 

to its effect in opposing t^e &ee discbarge of the water, 
and causing the land above it to be flooded during heavy 
rains. 

The dams on the Schuylkill navigation, and, indeed 
on many of the American rivers, are formed of timber 
firamework filled with nibble. That on the Schuylkill at 
Philadelphia, which served both for the navigation and for 




supplying water to drive the wheels of the Philadelphia 
Water-worfca, was formed in separate compartments or 
frames, each of which was 20 feet in breadth. These, 
ailer beiog framed together, were filled with stones, and 
sunk in the line of the dam. Fig. 20 is aa elevation, and 



fig. 21 is a section of the dam, from which its construction 
will be easily understood. The cribs were formed of logs 
of wood measuring 18 to 30 inches, connected together 
by strong dovetailing. The size of tiie framework in the 
direction of the stream waa 72 feet. The planking on 
the top waa 6 inches thick. The upper parts of the cribs 



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THE " BlVJJUt PROFEB OOHPABTUENT. X47 

were comiected together bo as to form one contmuons 
structure, and the whole was backed Vy^ a large mass of 
heavy rubbl& This dam withstood a flood, when the 
river Schuylkill was pasaiiig over it in a solid body of 
wateor, 7 feet 11 inches in depth without sustaining -any 
injury. 

The dams constructed l^ Sir W. Cubitt on the 
Severn are shown in fig. 22. They are formed of pUe 



» 



work and rough masonry, and have also withstood the 
flooda 

But the important question of flooding still remains 
to be noticed, and as Sir W. Cubitt very carefully studied 
that subject, I cannot do better than give what he laid 
before the Institution of Civil Eng^eers^ as the result of 
his experience : — 

" The problem proposed {he said) was this : a river 
which, from its source and the country it passed through, 
was liable to sudden changes of character — at one time 
running deep and rapid Hke a mountain stream, and then 
suddenly subsiding, and becoming so shallow as to impede 
the navigation, was required to be so improved as to 
retain the waters, that the TniniTmim depth, in times of 
> Vol v. p. 848. 



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148 INLAND NAVIGATION. 

drought, flhould be sufBcient for the traffic, and yet that 
the passage for* the flood-waters should be so ummpeded, 
that they should pass off, without unduly flooding the 
lands on either side of the stream, or injuring the drain- 
age. This was done by placing certain weirs obliquely 
across the main stream, their length being such as to 
permit of the fi^e passage of a body of water equal to 
the entire transverse sectional area of the river above the 
weir, without penning up the water so as to overflow the 
banks — the navigation being carried on uninterruptedly 
by means of locks, situated In lateral artificial cuts beside 
the welra By these means, however suddenly the water 
in the river rose and the banks were filled, the great 
length of the weirs enabled the flood to pass away, with- 
out reducing the average depth in the channel, yet allow- 
ing for the free drainage of the land above. 

" In placing a weir directly square across a river, a 
considerable portion of its section must be blocked up, 
and the water would be penned back, in proportion to 
the actual height of the weir and the area of the channel 
The water could never flow over that weir in a sheet wider 
than the channel, consequently, the depth upon the weir 
must be greater, and the 
tendency must be to 
block up the water, and 
even with a river bank- 
full an obstruction must 
exist. It would be seen 
by fig. 23, that if the breadth of the channel were ex- 
tended to three times its width, above and below, and a 



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THE "RIVER proper" COMPARTMENT. 149 

transvOTse weir placed, the same qxiautity of water would 
pass over, in a tilinner sheet, leaving a comparatively 
ttitnquil pool above the weir, which, if extended to a lake, 
would present the same appearance as the Lake of Geneva 
— comparatively still water, with a rapid river above and 
below it. It must be evident that the weir in this case 
offered no obstruction, as the 'v^ter waa enabled to pass 
more freely than along the river, either above or below. 

" Fig. 24 showed that the same end might be attained 

without the expense of 

cutting away the land, ] * '^"""'■■...^ 5 

by placing a weir of the Vm. 24. 

same length Id an oblique direction across the stream, 
without unduly widening the channel. The same quantity 
of water would pass in times of flood, and the velocity of 
the stream would be maintained more equably, than by 
any direct transverse obstruction. The greater the obli- 
quity the better would be the effect ; but, as a general 
rule, three times the direct width of the channel would, 
he thought, be an ample proportion, — ^in feet, it would 
seldom be necessary to give more than double the direct 
width. As a simple rule, it might be stated, th&t when 
the rectangle formed by the length of t±ie weir and its 
depth below the flood limit, equalled the rectangle of the 
river up-stream of the weir, within t^e same flood limits, 
then ramilar floods would not rise higher above these 
limits titan before the weirs were placed. 

" It had been attempted to be shown that the velo- 
city of the under-current would be checked, and that a 
depofflt would take place ; in feet, that the effect would 



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150 INLAND NAVIGATION. 

be analc^us to fiEing up the bed of the river to the 
height of the weiis, and that the deacendisg column, for 
a considerable distance up the river, would be materially 
checked. The contrary, however, had been the rrault. 
The surfece of the water had been prevented fix)m riaing 
during floods ; the bed of the river had not been raised, 
although dredging had not been resorted to ; and the 
drainage c^ the upper country had been fully maintained. 
The under-currOTit received no check, as, from the obli- 
quity of the weir, the stream was merely turned aside, 
and the body of the water rose gradually at its initial 
velocity. 

" Weirs, of the shape of a horse-shoe, and with an 
acute angle pointing up the stream, had also been tried ; 
but there were practical objections to both theee forms, 
as not leaving a free space within thran &r the over£Jl 
of the water, which there formed eddies, frequently scour- 
ing out the bed of the channel at the foot of tlie weir." 

Much difierence of opinion has berai expressed by 
engineers on the question raised by Sir W. Oubitt as to 
the relative obstruction to a river's flow presented by 
transverse and oblique weirs, and I am not aware that 
we possess any data determined by actual experiment. 
I think all eng^eers, however, agree on the advan- 
tage of the oblique weir in fiualitating the discharge; 
and meantime it is satis&ctory to know that the rule 
adopted by Sir William Cubitt, of making tlie weir of such 
length as thai the rectangle formed hy its length and its 
depth below the Jlood line ^mU be equal to the rectangle 
of the river above the weir within the same Jlood limits. 



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THE "BIVER FBOFER" COHFABTHENT. 151 

haa ffY&D. moot satia&ctory results on the SeTeixt, where 
weirs constructed on that principle have not increased the 
flooding of the river's banks. 

Oblique weira have also been emplc^ed with great 
advantage in the Shannon. Mr. Bhodea states that the 
weijs at EiUaloe and Meelick are each 1100 feet in length, 
that la summer water there is a flow of 6 inches, and in 
high floods fix)m 2 feet 6 inches to 2 feet 8 inches over 
their creeta, and they do not produce flooding of the lands 
above. 

Bhine and Danube. 
The works executed for the improvement of the upper rmpioTeni«nt of 

nppar portlou 

porti(»is of many of the continental rivers, such as the'>f<^tii>«Btai 
Bhine and the Danube, are veiy different in their char- 
acter &om those I have described. The continental rivers 
are lai^, and often occupy a wide-spreading bed, with 
numerous channels and islands, and in dealing with them, 
t^e Toam object of the engineer is to confine the whole of 
the water into one stream, in the certainty that, although 
the currents may be ioconveniently strong, there will be 
no difficulty in securing ample d^th for navigation. 

The works hktely undertaken on the Rhine, as de- RUne. 
scribed in the Proceedings of the Institution of CivU 
Engineers^ by Mr. Jackson, are of great extent, and were 
attended with much difficulty on account of the sudden 
floods, which, he states, occasionally in the course of 24 
hotuB rise to the extent of 38, and even 40 feet They 
consisted of cuts for straightening the channel— dams or 

■ Vol tU. p. 211. 



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152 INULND NAVIGATION. 

weire for checking the flow of the river — ^what are called 
diversion arms for separating the navigable channel, and 
spurs for directing ita course. It is worthy of notice that 
all these diversion arms and spurs are constructed of 
bundles of fescines, fixed by piles, and weighted with earth 
and stones — ^the distinctive feature of continental river- 
works. 
D«niibe. A short noticc of the Upper Danube, as given by Mr. 
Shepherd,' will serve to illustrate the nature of the works 
on such rivers. Mr. Shepherd says that the navigation 
was greatly impeded by the river shifting its course 
after ahnost every flood. Its channel was divided into 
numerous branches, and the main object of the improve- 
ments was to shut oS these lateral branches, and to 
cause the river to flow in one central channel The 
spurs formed for this purpose were projected from both 
banks of the river at such angles as were most suit- 
able to the line of bank and the flow of the stream, which, 
belQg always in the same direction, and not reversed by 
a flowing tide, is more easily directed and controlled. 



These spurs were constructed as shown in elevation 
fig. 25, and in plan fig. 26. The series of fiiscines of 
brushwood, a and b, are bound or woven together so as 

' deil EngineerM^ and ArckiUeta' Journal, toL xiL p. 321. 



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THE "biver propek" compahtment. 153 

to form one continuous line throughout the entire length 
of the spur ; each row is ■well secured to the groimd by 
short piles or stakes, and the space between each row is 
filled in with earth. The transverse fesoines, c c, are laid 



on the others, and also secured by piles — the ends to- 
wards the stream are left open, and their other ends are 
covered with earth, d d. When the main spurs extend- 
ing from the shore are completed, the arms of the river 
are dammed off in t^e same manner. 

Mr. Shepherd says that the rapidity with which the 
spurs are made is truly surpiising ; they offer but little 
resistance to the water, and as soon as the sand-banks 
begin to move, the debris is deposited between and in 
the spurs, which renders them immoveable ; the current 
at the same time is thrown into one channel, which has 
the effect of entirely scoiu-ing the river of the sand-banks 
previously deposited. 

The brmhwood is generally laid in such rivers in its 
green state, there to take root and grow again ; conse- 
quently, after a few years, each of the spurs forms a thick 
massive hedge, which prevents the stream from making 



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154 IHLAJIB NAVIGATION. 

further ravages on its banks, and con&ies it to one central 
channel, scotiring it out to a width and depth sufficient 
for all purposes of navigation. 

The dams or weirs on the continental rivers are gene- 
rally made of crib-work, such as has been described at 
page 146, a construction which seems very suitable where 
the currents are rapid. It is indeed wonderful what can 
be done in rapid rivers, having beds of shelving rock, by 
the judicious use of " crib-work " filled with stona By 
cautiously sinking and loading these cribs, and gradually 
extending their dimensions, a structure is at last ob- 
tained, of sufficient weight and base to withstand the 
destructive action of the currents, even in the most rapid 
streams, the open spaces of ike crib-work allowing the 
water to flow finely through ontjl enough of stonework 
is deposited to secure stability. The boldest of such 
structures I have seen is ihe foot-bridge leading to Goat 
Island, across the rapids of the Niagara. The river at 
the spot is said to have a gradient of one in fifty-two, 
and the sight, as viewed fix)m the bridge, of water tossed 
up by the ru^ed bottom into white-crested breakers, is, 
to an en^ew, rather su^^estive of a dangerous foimda- 
tioa Niagara, with its fidls and rapids, may truly be 
Bfud to be unique, but as it is possible thai, the device 
adopted to form the piers of the bridge may offer hints 
available for some engineering purposes, I shaU briefly 
describe the process as explained to me. The bridge was 
constructed by projecting l^iussed beams &om ihe shore, 
balanced by weights at their inner ends. Upright sup- 
ports were passed through holes in the outer ends of the 



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THE "EIVER proper ' COHPARTUENT. 155 

beama, and diiven down ao as to rest on the bottom and 
serve as temporaiy supports. Tlie beams thus tem- 
poiarilj placed, when planked, fonned a gangway for the 
workmen, who commenced to siak at the end of the 
beama a small fi'ame of open crib-work, which was filled 
with stones. Tiiis &bric, slender though it was, formed 
a more secure attachment for the ends of the trussed 
beams, so that heavy materials could be carried across 
them. Additional tiers of crib-work were successively 
built round the original core, until a mass was formed 
having sufficient base and weight to resist the force of the 
stream. Other piers were made In the same way, and 
thus the passage of the rapids was finally accomplished, 
the whole distance being about 400 feet. The only indi- 
cation of the rude manner in which the bridge had been 
constructed appeared in the somewhat zigzag line of the 
roadway stretching fit>m pier to pier, showing that the 
position of the piers had been fixed, not in accordance 
with any preconceived design, but to suit the rough sur- 
fitce of the river's bed, which, owing to the extreme 
rapidity of the currrait, could not previously be deter- 
mined by soimdings. Any attempt to sink a hollow box 
or cylinder, presenting a solid surfitce, in such a situa- 
tion, would, I fear, be hopeless, but open crib-work, 
allowing the water to pass through while it was being 
gradually loaded with stone, solved the difficulty, even in 
the rapids of Niagara, and a similar mode of construction 
has been found very useful in erecting dams and sinular 
works in many of the rapid continental rivera 



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CHAPTER VII. 

TroAL PROPAGATION AND TmAL COTIRENTS OF RIVEES. 

liDporUnoe of tidal flow — Its extent modified hf drcnnutMUMa— Tid»l wave — 
L*w« of ita pToptgation — Tidal cnirento — ObttMlM wbicli operate in re- 
tarding tidal waTe — Bore on tlie Dee — Bore on the Severn — Lerel of high 
water not raised by facilitatiDg tidal propagation. 

Tidal Navigation is a subject more intimately con- 
nected with the commercial intereets of the Sritish lales, 
and occupies a more important position in the hydraulic 
engineering of this country, than those branches of river 
navigation which we have been considering in the pre- 
ceding chapter. We have no great rivers here, like the 
Mifisiasippi, on which to launch and navigate the largest 
class of shipping. Our &esh-water streams, even by all 
the aid of weirs and locks, can hardly be made deep 
enough for canal bai^^es. The hills and valleys of our 
insular country have not sufficient area to form fresh- 
water streams available for navigation on a hu^ scale. 

The amount of water which our rivers dischai^ varies 
as the rain floods rise and fell ; and, even at their best, our 
navigable rivers and estuaries may be regarded simply as 
creeks or inlets, formed and kept open,. not by the fresh- 
water stream alone, but mainly by the action of the tide, 
and may be said to be navigable only when their channels 
are filled by the influx of water from the ocean. The 



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TIDAL PROPAGATION AND TIDAli CURRENTS. 157 

great agent in keeping open and deepening our naviga- 
tions is to be found in the tidal flow, which not only 
scours and maintains the sea-channels of our rivers, but 
also does important service by increasing the scanty depth 
of water which the river affords. Nor is this all : another 
most important advantage derived fiwm the tides is that 
upward current due to the tidal rise, which, at first 
checking, and ultimately overpowering and reversing the 
flow of the ebb-stream, carries vessels from the sea to 
their inland ports without the aid of either steam or 
wind. Even the most superficial observer cannot feil 
to recognise the value of this when he sees, on the Thames 
or any other tidal river, a vast fleet of vessels of all sizes, 
and from all coimtries, hurried on by the silent but power- 
ful eneigy of the flowing tide. How invaluable is such 
an agent to the commercial interests of this country I If, 
indeed, the action of our river-tides were suspended, and 
our coast begirt with a constarU low water, with all its 
attendant mud-banks and shoals, it might truly be said 
of the steam-power employed in our fectories and on our 
railways, that its occupation would be gone. I do not, 
indeed, require to do more to enforce the wide-spread 
interest of the subject than remind the reader that the 
ports of London, Liverpool, and Glasgow, not to name 
less important places, are entirely dependent on tidal 
navigation for their existence. 

From what has been said in Chapter III. as to the it> extant 
phydcal boundaries of rivers, it will be apparent that the oticDmBtaiice*. 
extent to which this tidal influence is felt varies in diflerent 
situations. Where the inclination of the river's bed is 



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158 INLAND NAVIGATION. 

gentle, and the chamxel is comparativelj dear and unob- 
structed, it is felt &r up tbe river, as in the case of the 
ITiames, where it reaches Teddington Weir, 65 miles fi:r>m 
the Nore ; and in the Tay, where it reaches its junction 
with the Almond, 35 milea from the bar. In other cases, 
such as the Lune in Lancashire, or Dee in Cheshire, 
the tidal flow is suddenly checked by artifidal weirs 
erected in the bed of the river for the use of mills. 
In a tiiird class of rivers the upward flow of the tide is 
almost neutralized by the existence of natural obstruc- 
tions, as in the case of the £me at BaUysbannon, where 
it flows only about three, and the Ness, where it flows 
only about two miles up the river. 

The tidal flow through estuaries and rivers gives rise 
to two phenomena, the one called "tidal propagation," 
and the other " tidal current," It is essential that the 
difference between th«n should be dearly understood; 
and it is further necessary that neither of them should 
be confounded with that vertical rise and fall of the water 
which is known as tlie range of the tide. 

Tidal Pbopagation. 

Tiu tidii wave. The tidal wave which enters an estuary is a branch of 
the great tidal wave of the ocean. Mr. Scott Bussell was 
the first 'experimental inquirer who conducted investiga- 
tions on the tide wave of estuaries, and gave the laws of 
its propagation, as deduced fivm experiments made on 
the Dee in Cheshire, and the Clyde, which may be stated 
as follows : — 

'^TlwrtiM. ^* '^® great primary wave of translation differs from 



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TIDAL PEOPAGATION AND TIDAL CURRENTa 159 

every other Bpedes of wave, in its otigin, its phenomena, 
and its laws. 

2. The tide wave is identical "viiih. the great primaiy 
v&ve of translation. 

3. In a rectangular channel, the velocity with which 
the tidal wave ia propagated ia equal to the velocity ac- 
quired by a heavy body fitlEng freely by gravity throng 
a height equal to half the depth of the fluid, reckoned 
from the top of the wave to the bottom of the channel. 
In a sloping or triangular channel the vdocity is t^t of 
a gravitating body due to 'Jd of the greatest depth. In a 
parabolic channel the velocity is that due to |ths or ^^ths 
of the greatest depth, according as the channel is convex 
or concave. And generally, the velocity is that due to 
gravity, acting through a height equal to the rfep(A of the 
centre of gravity of the transverse section of the channel 
below the surface of thejluid. 

4. The velocity in channels of uniform depth is inde- 
pendent of their breadth. 

5. A tidal bore is formed whrai the water is so shallow 
that the first fnives of flood move with a velocity so much 
less than that due to the succeeding parts of the tidal 
wave as to be overtaken ly the subsequent parts, or 
whenever the tide rises so rapidly that the height of the 
first wave of the tide exceeds t^e depth of water at that 
placei 

6. A wave of high water of spring-tides travels fester 
than a wave of high water of neap-tides. 

7. In addition to these laws stated by Mr. Buasell, I 
have found that the inclination of a river's bed, and of the 



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160 INLAND NAVIGATION. 

sulfide of the low- water stream, affect the rate of propaga- 
tion independently of the form or depth of the channel, 
and that, under certain conditions, a decrease of inclina^ 
tion is followed 1^ an acceleration, and an increase of 
inclination hy a retardation of the rate of propa^tion. 
But the results of my investigations will be best under- 
stood after I have described the works which afforded the 
data on which they are founded, and I shall defer further 
notice of them to a succeeding chapter. 

These laws, stated by Mr. Russell, are supposed to 
apply to the passage of die wave through channels having 
a pretty imiform depth and form of cross section ; but the 
very irregular outline of the beds of most of our tidal 
channels renders it almost always difficult, and in many 
eases impossible, to apply them ri^dly to cases which 
occur in actual practice. I may, however, state generally, 
in corroboration of the correctness of Mr. Russell's deduc- 
tions, that after investigating the tidal phenomena of many 
estuaries and rivers, I have found that in all cases the 
quickest propagation of the tidal wave occurs at those 
places where there is the greatest average depth; but 
the varying outline of the cross section renders it almost 
impossible in most cases to determine what is the ruling 
depth for calculating the rates of propagation in any 
particular section of the river. In the Dornoch Firth, to 
which I have already alluded, I found that the distance 
(rf 1 1 miles between Portmahomac and Meikleferry is tra- 
versed by the tide wave in 30 minutes, being the interval 
between the first appearance of the tide at the two stations, 
giving a velocity of 23 miles per hour. The depth of 



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TIDAL PROPAGATION AND TIDAL CURBENT8. 161 

water of that part of the firth Taries from 9 to 50 feet. 
Between M^klefeny, again, and the Quarry, a distance 
of 8 miles, where the depth is much less, varying fix)m 6 
to 20 feet, the transit of the wave occupies 65 minutes, 
giving a speed of 6'4 miles per hour. Between the 
Quarry and Bonar Bridge, a distance of 1 mile, the water 
is comparatively shallow, varying from 1 to 3 feet, and 
the rise in the bed of the river is veiy rapid. In conse- 
quence of these obstructions the tide does not appear at 
Bonar Bridge for an hour and a half afrer it has appeared 
at the Quarry, giving a rate of propagation of only two- 
thirds of a mile per hour. 

Tidal Cuehents. 

But iioB passage of the tidal wave through an estuary 
or river must not be mistaken for the other phenomenon 
to which I have alluded, called the " tide current," which 
is totally distinct in its origin and character. The tidal 
wave which I have been describing as passing through 
the lower part of the Dornoch Firth, fiir example, at the 
rate of 22 miles per hour, is not that current due to the 
flowing tide by which vessels are carried across the bar, 
and borne onward to their destination. That current 
at the Dornoch Firth flows with a velocity which I never 
found to exceed 4 miles per hour. The laws of the pro- 
pagation of the tidal waves, to which I first alluded, 
depend, as explained, on drcumstances somewhat obscure ; 
but the velocity of the tide current, or that current 
which flows iato our rivers, is due entirely to the slope or 



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162 INLAND KAVIQATION, 

fcJX on the surface of the water. The amount of this slope 
depends on the rapidity with which the tide risee and the 
degree of obstruction presented to its propagation up the 
river. The more rapid the rise of tide and the greater 
the obstruction to its flow the greater will be the differ- 
ence of level in the tidal lines, as shown in the plates which 
illustrate Chapter lY. A head of water is thus formed, 
whose height is due to Hhe rapidity of t^e rise of the tide 
and the obstruction to its progress ; and a flow of water 
having a velocity due to that head is generated up, or 
perhaps I should say itUo, the river or estuaiy, and this 
flow of water is what I term the flooclrtide current. A 
similar slope or &11 occurs on the sur£tce of <^ ebbing 
tide, due to the depression of the level of the sea at the 
mouth of the river, which again causes an ebh tided 
current, flowing in the opposite direction. 
obataciM wiiicb Now, the obstructions which are most firequently found 
t«urdiDB tidal to retard tidal propagation, and to produce a heaping up 
of the water and rapid tide currents, are the circuitous 
routes of the channels of rivers, inequalities in their beds, 
the projection of obstacles from their banks, and in certain 
circumstances the slopes of their sur&cefl. The combined 
effect of these obstructions is such as in all rivers to che(^ 
the propagation of the tide-wave, and, in situations whero 
there is a great and rapid rise of tide, to heap up the 
water in the lower part of the river during flood, and so 
to occaaon what are termed " bores," and other apparent 
anomalies. In. the chapter on Tide Observations I 
directed attention very fully to the existence of this heap- 
ing up of the tide during flood, but I did not then direct 



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TIDAL PROPAGATION AND TIDAL CDBEENTS. 163 

attrition to the cause and conBequeiices, of which I hare 
DOW to speak. In the Dee, as has already been stated, 
there is at low water a fiill of 11 feet from Chester to 
Flint, a distance of 12 miles ; and on one occasion I found 
that after the tide had risen 18 feet 4 inches at Flint, it 
had not commenced to flow at Chester. While, therefore, 
at low water there is a fell seawards of 11 feet from 
Chester to Flint, there was at the time alluded to a fell 
from the sea downwards, so to speak, of no lees than 7 
feet 4 inches from Flint to Chester. Fig. 27 is a diagram 




of these tide lines, which will illustrate more clearly the 
effect of this heaping up of water in the seaward part of 
the tiver. The lower line represents the surfece of low 
water, and the upper line shows the 8urfex^e at the period 
of flood-tide to which I have idluded. In this case the 
small depth of water, and tortuous and unequal channel, 
retarded the early waves of flood-tide so much, that they 
were overtaken by the succeeding waves ; and, in accord- 
ance with Mr. Russell's theoiy, a tidal bore was the 
result, or, in otJier words, the water was heaped up so 
high, and the slope was consequently so great, as to cause 



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164 INLAND NAViaATION. 

the water to tumble over, and ascend the river in the 
form of a breaking wave. 
■nmpiBofk The manner in which such tides flow up an estuaiy 

umDm. may probably be made more intelligible by a simple 
description of a flood-tide on the Dee than by diagrams of 
tidal lines. In fig. 28 the letters a, h, c, d represent a 
part of the low-water channel of the river Dee, at a place 
where the estuary is about 3 miles wide, and consists of 
extensive sand-banks. In examining minutely the wind- 
ings of the stream in reference to certain investigarions, it 
was necessaij to walk down the right bank of the river 




at low water, close to the edge of the channeL While so 
engaged, I crossed at the point h, a hollow in the sand- 
bank, which, though depressed below the general height 
of the surrounding sur&ce, was nevertheleBs quite dry, 
the lowMt part of the track being considerably above the 
level of the water of the river. Crossii^ this hollow, the 
noise of the approaching tide vrm heard ; and expecting 
to meet the flood forcing its way up the river, I continued 
to walk on towards c ; but seeing no appearance of its ap- 
proach by the proper channel, and still bearing the noise 



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TIDAL PBOPAQATION AND TIDAL CURRENTS. 165 

giaduallj mcreaaiiig, and apparentlj coming fix>m beliiiid, 
I turned round and perceived a rapid run of vat^ flowing 
(in the direction shown by the arrow) through the hollow 
deb, which had just been crossed, and emptjing itself 
into the river at b. I immediately hastened back, and 
after having waded through the newly-formed stream 
at b, which had attained a depth of 6 or 8 inches, 
I remained on its upper side to see the result of this un- 
expected inroad. The water continued to rush through 
the hollow, rapidly gaining breadth and depth, and 
at last, after an interval of 2 or 2^ minutes from the 
time at which the noise was first heard, the tide appeared 
forcing its way up the proper channel of the river, 
with a head or bore of 6 or 8 inches in height. In 
this case it is dear, from what has been said as to the 
slope on the river from Flint to Chester during the early 
periods of tide, that the level of the water at cf in the 
diagram would be above that at b. The tide, on arriving 
at the point d, would be naturally divided into two 
branches or currents, one proceeding up the natural 
channel towards c, and the other flowing into the hollow 
in the sand-bank at d towards e ; and as the level of the 
water at d rose, the stream which flowed into the hollow 
in the sand-bank would gradually rise higher xmtil it sur- 
mounted the summit-level at e, o&er which it would rush 
from e to & without obstxuction. The other branch of the 
tide would in the meantime be forcing its way along the 
circuitous channel deb, which was about a mile in length ; 
and before it reached b, the water at d had attained a 
much higher level than at b, and having surmounted the 



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166 INLAND NAVIGATION. 

summit-level of the sand-bonk at e continued to flow 
without obstruction into the channel of the river in the 
manner repres^ited. From this I draw the general con- 
clusion, thcit in all places where the retarding influences 
which exist in the regular channel of a river exceed the 
obstructions in any hack lake or swash^^ay, the tide wiU, 
fiow sooner through the latter than the former, and give 
rise to an apparent anomaly of two tides ^flowing in 
opposite directions, in the same river, till they are neutra- 
lized by coming in contact. 

The late Admiral Beechey, in hia Remarks on the Tidal 
Phenomena of the River Severn, published in 1851, gives 
the following interesting accoxmt of the bore on that 
river : — " The bore," he says, " is not dangerous to boats 
if afloat in the middle of the river ; and it is the common 
practice up the Severn to row the boats out to t^e centre 
of the stream on the approach of the bore, and put theor 
head to the wave ; but if this precaution be not taken, 
and the boats are allowed to remain at the edge of the 
shore, they are liable to be swamped or stove, as the 
wave breaks with great violence along the banks as it ^o- 
ceeda ; but towards the centre of the river, if the water 
be not very shallow, the wave is smooth and unbroken. 
Before the arrival of the bore, the stream runs down the 
river, and the altitude of the water at a distance from the 
sea is quite stationary ; but on the arrival of the bore the 
water instantly rises according to the height of the breast 
of the wave, and the stream turns and follows the wave 
up the river, although it had but a few minutes before 
been running down at a rapid rate ; and this change of 



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TIDAL PROPAQATION AND TIDAL CITBRBNTB. 167 

stream is efiected without any breaking wave. When 
there is a heavy fresh down the river, and the stream is 
running at tiie rate of four or more miles an hour, the 
upward Ettream hanga for several minutes after the bore 
has passed, not being able to overcome at the moment the 
impetus of the ebbing water; but whoi it has once 
turned upwards, it attains its mftTimnm speed in the £rst 
half hotnr of the tide. "When the reaches of the river are 
stnught, the bore travels evenly up the river, but at the 
turnings it is thrown o£f towards the further dde, where 
it rises higher than in ihe straight reaches ; thence it 
recoils and impinges upon the opposite shore, and so, like 
a disturbed pendulum, it osciUates from side to side, and 
only r^ains its steady course when the reaches lengthen. 
The highest tide of the year rolled up the Severn on the 
1st of December. There was about 2 feet of wat«r above 
the ordinary summer-level in the river, and the morning 
was calm and &vourable to the phenomenon. The st^-eam 
at low water ran down at the rate of 2^ miles (geographical) 
per hour, itntU the time when the bore came rolling up 
the river with a Inreast from 5 to 6 feet high at the eddee, 
and 3 feet 6 inches in the centre. The wave was glassy 
smooth ; and as it advanced towards a spectator stationed 
at Stonebench, a singular effect was produced by the dis- 
torted surface of the wave reflecting the rising sun, and 
brilliantly illuminating the stems and branches of the 
wood skirting the river as the bore passed along — an 
eflfect which greatly enhanced the interest of the pheno- 
menon, 'which is at all times an object of curiosity. The 
stream tiuned up the instant after the bore passed, and 



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168 INLAND NAVIQATION. 

ran at the rate of 3f miles per hour, which was about 
half the average rate of the bore, the speed of which 
varied from 12 to 7 miles per hour, averaging 8 between 
Stonebench and Gloucester." Admiral Beechey fiirther 
says, " that the effect of a fresh, or a certain depth of 
water in the river, upon the advance of the bore, is 
remarkable. At dry periods the great obstruction to the 
progress of the bore lies between Sharpnesa and Bollow- 
pool, and at such times the many dry saud-bfoiks prevent 
the bore attaining a rate greater than about 4 miles an 
hour ; but when the river is under the influence of freshes, 
and the water raised, covering some of the banks, it 
appears to roll on at a rate of 10 miles an hour in oppo- 
sition to the stream, which runs down at the rate of up- 
wards of 4 miles an hour." 

The phenomenon of the bore, called mascaret by the 
French, and in South America j^ororoca, has been reported 
by sotae travellers to assume dimensions hardly conceiv- 
able. Condamine, in describing that of the Amazon, says,^ 
" At the distance of a league or two a frightful noise is 
distinguished, the herald of the pororoca, which is the 
name given by the Axaericans of the district to this 
tremendous bore. In proportion as it advances the noise 
increases, and shortly a promontory of water is seen, from 
12 to 15 feet high, whidi is succeeded by a second, after- 
wards another, and sometimes again a fourth, rapidly im- 
pelled one after tlie other, and fllling the whole breadth of 
the channel ; this bore advances with prodigious rapidity, 
and carries away before it whatever opposes resistance." 

* Pinkerton, Travel*, roL ziv. p. 262. 



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TIDAL PBOPAGATION AND TIDAL CUREBNTS. 169 

But to return to our own rivers : the object of the engi- 
neer in dealing with what I have termed the tidal com- 
partment, is to &cilitate the propa^tion of the tidal wave 
through the estuary or river, for whidi he has to design 
works, so as to increase the tidal influence, and also to 
decrease the tendency to the heaping up of water in the 
lower reaches of the river during flood-tide. The heaping 
up of the tides, and the bore it occasions, will readily be 
admitted to be a great evil, and if my remarks aa to our 
rivers being navigable only when they are supplemented 
by the presence of the tide be true, it will be no less 
obvious that all extensions of the period during which iho 
tide is operative must be a great advantage ; and this is 
what I mean by increasing the duration or ir^uence of 
the tide. It will be found, I think, in the examples I 
have hereafter to offer, that, with proper management, 
these desirable results may be surely accomplished, and 
the amount accurately determined. 

This is probably the most convenient place to notice 
some hcta of great importance in Kiver Engineering, 
which I deduce from these considerations as to the nature 
of the tidal propagation and tide currenta The obstruc- 
tions to which I have alluded retard the rate of pro- 
pagation, but they increase the velocity of the tide 
currents. Now, as the aim, and, if Buccees&il, the effect 
of all engineering works, is to increase the rate of tidal 
propagation, no lees certainly wUl th^ tend to Irasen the 
heaping up of water in the lower reaches, and at the same 
time to decrease the velocity of the tide currents. In 
cases where these currents are found to act prejudicially 



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170 INLAND NAVIQATION. 

by producing a bore, or by bringing up sand from the 
lower parts of the estuary, or where they are inconveni- 
ently jiapid for navigation, we are thus, while increasing 
the propagation of the tidal wave, enabled to check thwr 
^leigy, and thus to effect an important improvement. 
Tbaicvaiot AnothoT clrcunistance is worthy of notice. It is 

niiedbrficm- well known that the momentum of the column of water, 

Uting tidal pro- -. . -i-n . 1--11 

pagkUon. flowing Up the gradually contracting and n^ng channel 
of a river, causes the level of high water to stand 
higher than in the open ocean or in the lower reaches. 
This is accounted for, as already stated, on the principle 
of the conservation of forces. The height to whidi the 
water is thus rused depends on the quantity of water 
thrown in by the tide during a given time, the elevation 
being greatest at spring, and smallest at neap tides, as 
I have shown at page 83. At the Dee, for example, I 
fotmd that the high water of spring-tides at Chester was 
14 inches higher than that at Connah's Quay; while at 
neE^-tides the difference of level was only 4 inches,^ 
From observations given by Admiral Beechey it appears 
tikat the high water at Shatpness is sometimes 10 &et 8 
inches higher than at Minehead, the (^stance between the 
places being 66 miles. But the rise of tide in the Bristol 
Channel is very great, and Ita tidal phenomena peculiar. 

In conndering the elevation of the level in the upper 
part of a river, as a mechanical question. Dr. 'WheweU 
says it may be accoimted for by what is called "the 

' AdminI Beschey foaiid Out at tha Severn the low watar of ipring tidea 
doe* not fall ao low aa that of oeapa, which he attribatea to the greater qtuDtity 
of tidal water oot having time to flow ont. I ain not »wan of a aimilar obaerra- 
tion having been made at any other plaoa. 



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TIDAL PROPAGATION ANB TIDAI, CURRENTS. 171 

principle of the conservation of force. When any quantity 
of matter is in motion, its motion is capable of carrying 
every particle of the mass to the height from which it 
must Have fallen to acquire its velocity; but if the motion 
be employed in raising a smaller quantity of matter, it is 
capable of raising it to a height proportionally greater. 
In bays and channels, which narrow considerably, the 
quantity of water raised in the narrow part is lees than 
in the wider, and thus the rise in such cases is greater."^ 

Now, as the ^ect of engineering works, as will be 
more fidly detailed hereafter, is not only to produce a free 
propagation of the tide, but to admit a larger body of 
' tidal water, it has been contended that such operations 
must necessarily cause the tide to rise higher, and it has 
been attempted to be shown in some cases in my own 
experience that they would necessarily occasion incon- 
venience, and even injury to property, by the improved 
river rushing up with violence and overflowing its banks. 
After the most careful observation, however, I have 
not been able to detect that such operations have, in 
any case, had the effect of notably raising the level of the 
high-water line. The tide, in improved rivers, begins to 
flow earlier than before, and a larger body of water is 
carried up the navigable channel, where its eflect is most 
useful, but the same works which increased the propaga- 
tion have, hy removing obstructions, decreased the heaping 
up of the tide, and, consequentiy, the velocity of the tide 
corrent ; and by this fortunate compensative action, our 
rivers, though their beds are opened up and improved, do 
> PhUotaphical TnmtaeUoiu, 1833, Pl 2M. 



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172 IKLAiro NAVIOATION. 

not inundate our towns, or even overflow our quays, but 
quietly keep within their original limits. That such im- 
provementa, by a£brding a more rapid discharge at ebb- 
tide and low water, have diminished the extent of land 
floods, cannot, I think, be doubted. At Glasgow, the 
floods do not now flood the Green and the low-lying 
streets in that locality as they used to do ; and at the 
Tees, Mr. John Fowler, the engineer to the Navigation 
Trust, says that previous to the improvement of the river 
the lower parts of Stockton were frequently flooded, and 
in the High Street of Tarm, which is 8 miles above 
Stockton, the water often rose 5 or 6 feet, but since 
the execution of the works there has been no such flood- 
ing. But this land flooding, the reader will bear in mind, 
is in no way connected with the tidal phenomena which 
we have be^i considering. I have, however, noticed it, in 
passing, as an effect of river improvement. 



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CHAPTER VIII. 

TIDAL COMPABTMENT — ^WOEKS FOE ITS IMPEOVEMENT. 

B«moTml of obrtrnctioiu to tidal flow — Wetn raeoted for public vrorki — Work* 
for improTement of tidml oompartmaiit of riven — Itt, Eemoval of lateisl ob- 
•tmotioDB ; jsttiM objectioiiBbIa ; pien of bridges obJMtioiuble — 2d, Tntitiing 
mils ; Bibble l<nr-w*ter trMning mlla ; coinparatiT'e adTmntagea of ttrught 
and mured walla; fonn and oonstrDotion of river walla — 3d, Clodog of anb- 
aidiary channela — UA, Snbititutiiig straight ontt for benda — 6(A, Dredging ; 
its iubodDotion ; bag and spoon dredge ; backet between two lighten ; iteMn 
dredges ; hand dredges ; dredging on the Clyde and Wear ; improvementa in 
steam dredgea ; dredging on Amaterdam and 8nea Canals ; longitudinal and 
cToaa dredging ; blasting at BaUyshannon, at the Severn, and at St. Helien, 
Jeney ; dredging in eipo«ed situations — StA, Eioavation ; by diving-bell ; 
by floatation ; by oofferdams — Tri, Sconring — StA, Kedodng the inclination 
of the bed. 

The removal of all obstacles to the flow of the tide Bemovai of 
13 the object, as already stated, to which attention has ^ tidai Ho*. 
chiefly to be directed in deedgning improvements in the 
department of navigation we are now considering ; and 
in order to form a satisfectory opinion, it is necessary to 
have an accurate survey, showing the depths of water and 
the breadths of channel throughout the whole extent of 
tlie river, as well as the amoimt of tid^ range, the velocity 
of the currents, the rise on the bed, and the nature of the 
materials of which the bottom and banks are composed, 
as explained in the chapter on Hydrometric Observationa 
Possessed of this information, iJie engineer is in a position 
to consider to what extent the bed of the river may, with 
advantage, be deepened and widened, and the currents 



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174 INLAND NAVIGATION. 

directed by means of walls; also whether suheidiaiy 
channels may, with safety, be shut up, or new cuts be 
made for the passage of the river, or whetlier or not 
irregularities in the width, which injuriously affect the 
currents, may be corrected. The effect of su<^ works 
will be to cause the ciurents of flood and ebb tide to flow 
always in one channel, and thus to exert their flill and 
combined power in keeping open one navigable track. 

Before, however, proceeding to describe these works, 
it is perhaps proper to notice the artificial weirs that in 
some tidal rivers have, in early times, been erected for 
the purposes of manufacture. The removal of such erec- 
tions, however prejudicial they may be to navigation, is 
in many cases attended with difficulty, owing to the great 
value of the interests involved, and the lat^ compensa- 
tion ckdmed by proprietors. Sudi weirs, for example, 
are to be found on the Dee in Cheshire and the Lime in 
Lancashire, and other rivers ; and in order to show iheai 
obstruction to the tidal flow, I have only to state the 
&ct8 as regards the weir on ihe Dee, which was erected 
at an early date for supplying water-poiyer for Chester 
mills. I had occasion to examine it with reference to 
the extenmve flooding of the meadow-lands on the banks 
of the river above the weir, and fotmd that its crest was 
11 feet 6 inches above the bed of the river inmiediately- 
below it, and that the level of tiie crest, if extended up 
the river, does not strike the bed for a distance of 7 
nules. It thus presents a perpendicular &ce to the flow- 
ing tide, which is completely checked until it rises so high 
as to reach to the top of the weir, and this happens only at 



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TIDAL OOUPABTHENT. 175 

high spring-tides. The weir, therefore, forms an artificial 
pond in the river's bed of ^ miles in length, which, were 
the obstacle removed, would be £Ued and emptied as 
the tide flowed and ebbed, and thus the scouring power 
of the river would be increased. But the vested inter- 
ests of the mill-ownerB cannot be violated. 

The removal of existing quays and other works of long 
standing, as in the case of the Tyne, the Wear, Eind other 
rivers, is also for the same reason difficult, and works 
must oftrai be designed for such localities which shall not 
injuriously afEect existing property, unless, indeed, as in 
the cased of the Thames betwerai Westminster and London 
Bridge, and the Fojle at Londonderty, whoe the rights 
of all proprietois were purchased, and a line of quays 
formed to meet the public convenience irrespective of 
private interests. 

These weirs and quays, however, present difficulties, 
which may be regarded as financial rather than engineer- 
ing, but I have thought it right to notice them, in passing, 
and shall proceed to consider the works which will be 
found to be generally applicable to riv^ improvements, 
under the following heads : — 

1. Bemoval of lateral obstructions. 

2. Training walls. 

3. Clodng of subsidiary channels. 

4. Substituting straight cuts for bends. 

5. Dredging. 

6. Excavation. 

7. Scouring, 

8. Bedudng the inclination of the bed. 



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176 INLAND NAViaATION. 

1. Removal of Lateral Obstructions. 
Under the " Removal of Lateral Obetmctions " may 
be classed all those works which have for their olg'ect the 
formation of proper outlines for the banks or sides of the 
river. In the early history of river engineering it was 
conmion to construct jetties or groins projecting from the 
banks on either side, with the view of narrowing the 
stream, and producing a greater scouring power to operate 
on the bottom. It is no doubt true that such projections 
have the effect of producing a local acceleration of the 
currents, and in soft bottoms a corresponding increase of 
depth in their immediate vicinity. But this increase of 
velocity and depth being due entirely to the obstruction 
and consequent raising of the level of the water caused 
by the jetty, is strictly local Whenever the water passes 
the end of the jetty, it expands into the greater width 
of bed, the head is reduced, a stagnation or eddy takes 
place, and a bank or shoal is formed — a result which 
invariably follows the projection of any obstruction or 
foreign body into a stream having a soft bottom. I have 



^"■*™rA'* ■«* ""n- iiiT*ii ym idlfHim. '^nr 



often observed this on the river Dee, in Cheshire, where 
there is a long straight reach with jetties projecting from 
one side, and a continuous embankment on the opposite 
side of the channel, as represented by iiie dark lines in 



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TIDiL COMPABTMENT. 177 

fig, 29, which is a small portion of the Dee at low water, 
the direction of the current heing shown by the arrow. 
From this cut it will be understood that at the ends of 
the two jetties there are holes 12 or 14 feet deep at low 
Tra.te(r, while a sand-bant or shallow, nearly dry at low 
water, extends into the river between the jetties. The 
manner in which the tidal current is distorted by the jet- 
ties is shown in fig. 30, which represents the same portion 
of the Dee during the flowing tide. The current, indicated 



by the lai^ arrow, on reaching the jetty A, is obstructed, 
and consequently the level of the sur&ce is raised, so that 
the water on the seaward mde of A is some incies higher 
than on its landward side. The sur&ce of the river at B 
is also nused, and a strong current is generated past the 
end of the jetty, which curls round into the space between 
the jetties A and C. The main strewn passing on, im- 
pinges against the jetty C, raising a head at its seaward 
side, and a corresponding current towards the shore C A, 
along which it flows, and toward the root of the jetty A, 
where the level of the water is also low. The whole of 
this complicated motion takes place in not veiy many 
seconds, and the result is a counter-current and eddy 
between the jetties ; and this action continues during the 
whole flow of the tide, and is more or less marked accord- 



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178 INLAND NATIGATION. 

ing to the strength of the current ; for it must be remem- 
bered that the depression on the upper sides of the jetties 
ia not immediately filled up by the rush of water round 
the extremity, because the head which produces the velo- 
city continues to increase with the rising tide, and the 
effect shown in fig. 30 will continue until slack tide, when 
the surface of the water above and below the jetties attains 
the same level A similar action, the directions of the 
currents being reversed, takes place at ebb tide, and in a 
river with a sandy bottom like the Dee, it is not diflScult 
to imagine the consequence of such a disturbance of cur- 
rents in excavating holes and throwing up shoals. 

As an aggravated instance of the tendency of all ob- 
structions to produce currents and distortion of the bed 
of a river, I may refer to a vessel of about 170 tons, 
which, by the breaking of a tow-line, grounded in the 



Tay when there was some flood in the river. The con- 
sequence of this mishap is shown in fig. 31, where the 
vessel is represented at a as lying in a pool which was 
scoured to the depth of 10 feet in the course of a few 



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TIDAL COHPABTICENT. 179 

tidefl ; and the gravel thus excavated by the current, act^ 
ing on the grounded vessel, and amounting to upwards of 
1000 tons, was deposited in the form of a bank 5 feet 
above low water immediately below the pool, as shown in 
hatched lines. Thus, although the cnrront in its natural 
state was not suffidently strong to act on the bed of 
the river, the foreign body or obstruction caused by the 
grounded vessel raised a head of water which produced a 
current powerful enough to excavate hundreds of tons of 
gravd in a few houra A similar effect, though varying 
in d^ree, occurs in all rivers confined by jetties, such as 
iJiose on the Dee, to which I have referred. Bivers so 
treated present an alternation of shoals, nearly dry at 
low water, and deep pools instead of a r^;ular bottom 
and a uniform depth of water available for the ptuposes 
of navigation ; and it is wonderful how long the system 
of " jettying," or, as it is termed in England, " cauling " 
a liver continued to be advocated and followed by 
engineers. The Clyde, Tyne, Tees, and othar rivers, 
suffered, if I may use the expression, &om jetties, con- 
structed at great ezpraise, intended to confine and im- 
prove, but which rather tended to distort their channels. 
On the Clyde and some other rivers the ends of the jetties 
were latterly connected by longitudinal walls, which no 
doubt, to some extent, obviated the evils described as pro- 
duced by the jetties on the Dee. But still it was long 
generally believed that jetties must, in the first instance, 
be constructed, even although their extremities might 
afterwards be connected with longitudinal walls if neces- 
sary. From the Clyde, the upper part of the Bibble, the 



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180 TNLAITD NAVIGATION. 

Tay, and the Tees, and other rivers they have been 
entirely removed. I have universally found that, 
wherever jettiea existed, their entire or partial removal 
formed one of the first steps towards an improvement 
of the navigation, being, in all cases which have come 
within my experience, followed by good results ; but I 
am not prepared to say that there may not be some 
special case in which a jetty may be advantageously 
employed in a navigable channel, indeed, I on one oc- 
casion recommended it, to reduce an undue width of 
i^iannel, where circumstances connected with access to 
the land prevented the formation of a wall, and, of course, 
for other purposes, such as the protection of a river's 
banks without reference to navigation, they are often 
found to be very useful. 
Vim of bcidgM What I have said as to the injurious effects of jetties 
applies with equal force to the piers of bridges erected 
across tidal rivers. 

At the bridge over the Lary, near Plymouth, erected 
by Mr. J. M. Bendel, it was found that the scour was 
operating injuriously on the bottom, and he applied an 
artificial bed of clay from 18 inches to 2 feet thick, 
covered with stones of all sizes from 200 lbs. downwards, 
to protect the clay from the run of the water, the clay 
having a good effect in preventing the stones from 
being moved ; the combined thickness of the clay and 
stones was from 2 feet to 2 feet 6 inches, thus replacing 
the loss of the natural bed which had been scoured away. 
This artificial bed was found to be quite successful, and 
resisted a current of nearly 5 miles an hour. Messra D. 



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TIDAX COMPABTMENT. 181 

and T. Stevenson suggested the same remedy for iixe rail- 
way bridge at Inverness, where scouring to the depth of 6 
feet had occurred. In both cases, the original bed being 
restored, the velocity of the currents waa increased by 
the reduction of water-way due to the piers of the bridge. 
But in navigable rivers it is not always demrable to in- 
crease the velocity of the current, but rather to found the 
piers so low as to place them beyond risk of injury from 
scouring. As an instance of this I may mention tihe rail- 
way bridge acroes Uie Foyle at Londonderry. The scour- 
ing which took place there operated chiefly on the eastern 
or concave rade of the river, and the deepest cavities were 
in immediate proximity to the |ners of the bridge, — 
results which, from what I have stated as to the Dee, 
would naturally happen. The greatest depth scoured 
from the bed of the river was about 4 feet betweai the 
piers, and increased at the piers themselves to about 8 
feet The transverse section of the river showed that t^e 
abrogate width of the piers of the bridge and side-walls 
was 150 feet, being about a silth of the whole width of 
the river at the pla>ce in question. The sectional area of 
the river previous to the erection of the bridge was 
18,079 square feet at half-tide, when the current is 
strongest, and the piers occupy a space of 2475 square 
feet, reducing the sectional area of the river by that 
amoimt. It is obvious that in all such cases, if an equal 
quantity of water is to flow into the upper part of 
the river in the same time as before the erection of a 
bridge, the velocity of the currents must necessarily be 
increased in proportion as the sectional area is diminished. 



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182 INI.ua> NAVIGATION. 

This increased cuireiit, acting on the soft* bottom, must 
graduallj gain in depth what has been taken from the 
water-way in width, and whenever the deepening is suf- 
ficient to compensate for the diminution of sectional area 
caused by the piers, the scouring action will cease. The 
sectional area occupied by the piers of the Foyle Bridge 
at half-tide was, as abready stated, 2475 feet, and ihe 
sectional area scoured fix)m the bed of the river was about 
1868 square feet, and in reporting on the subject to the 
Harbour Commissioners it was stated that the scouring 
might be expected to continue until the increased 
sectional area should have so &x diminished the velocity 
of the currents as to render them inoperative on the bed 
of tJbe river — a result which has since been verified ; and 
as the piers of the bridge had been carried by Mr. Hawk- 
shaw, who was engineer to the railway company, upwards 
of 30 feet below the bed of the river, the stability of the 
structure was not affected, and the velocity of the tides 
through the opening draw of the bridge, made for the 
passage of ships, was not increased. A wimilnr result hap- 
pened at the railway bridge across the river Tay, where, 
&om sections made in 1847 and 1849, before and after the 
bridge was built, it appeared that the bed of the river, 
which consisted of gravel, had been scoured to the extent 
of 2 or 3 feet, and that it ceased whenever the normal 
proportions between the quantity of water passed and the 
sectional area were restored. In a river like the Tay, 
where the bottom is gravel, it may &irly be assumed that 
when the scour of high floods has enlarged the water-way 
the bed of the riv^ will continue unaltered, because the 



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TIDAL COHPABTMENT. 183 

material that haa been scoured out is so heavy that only 
the velocity of a heavy land-Jlood can move it, and, there- 
fore, the mere flow of the tide cannot again disturb it. 
But in rivers having soft beds, composed of fine sand or 
silt, easily moved, the matOTial scoured by land-floods is 
brought back by the flood, and thus it is impossible, when 
piers or other obstructions, such as jetties, are placed in 
rivers with sofb bottoms, to preserve a uniform depth of 
water, as it changes from fortnight to fortnight with the 
constantly changing velocities of neap and spring tides. 

The only other remark which I have to ofier on this 
section of works is, that in some instances where the 
river is contracted 1^ the projection of quays, or by the 
natural formation of the banks, it may be found advisable, 
where it can be done consistently with existing interests, 
to enlarge the cross-sectional area iii order to reduce the 
velocity of the currents, and prevent disturbance of the 
tidal flow. Indeed, it may be laid down as a general 
principle in designing works for river improvements, on 
ike one hand, not to adopt a VKiter-way so great as to 
reduce the scouring power and produce shoaling, nor, on 
the other hand, so smaU as to increase the current beyond 
«Aa( is convenient/or the proper ma/nagement of vessds. 

2. Training Wails. 
In open estuaries filled with sand-bfoiks, the courses 
of rivers are liable to constant alteration, due to every 
change in the tides or winds. The woodcut of the Lune, 
fig. 32, illustrates this remark. The several dotted lines 
represrait the variations of the river during ihe period of 



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INLAJ*D NAVIGATION. 



^^^ 


*"v? 


^w 


-! 


Iff 




c^^ 








i^^^S 








Co- 








! 


^-"i 


■■•'■■-'?. \ 


WT^ 


-j^ 



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TIDAL COMPARTMENT. 185 

a few years. This tendency to deviate from channel to 
channel is common to all rivers that are left, imdirected, 
to work their way through a tract of sand, and is utterly 
destructive to navigation. Continued during every flood 
and ebb tide it sets loose a large amount of floating sand, 
which is daily drifted to and fro, and deposited in some 
new Estuation. A channel which is thus constantly 
shifting its course never remains sufficiently long in one 
position to form for itself a properly defined bed, but is 
in &ct always in a transition state ; the sand which is 
worn from the concave side, where there Is the greatest 
scour, b^ng thrown to the convex side of the stream, 
while some portion of the floating materials, carried to 
and fro during this process of perpetual change, is oft«ai 
deposited, and forms shoals in the middle of the &ir\my. 
A river left in this state of nature cannot possibly attain 
the mcadmum depth due to the natiual scour of the tidal 
currents, as their power is expended in abrading and 
removing the sand-banks through which the stream flows, 
and not, as it ought to be, in deepening and scouring its 
bed. In such cases what is wanted is to secure a per^ 
manent channel, by guiding the first of the flood and the 
last of the ebb tide by means of walls, so that the strength - 
of the currraits may constantly operate on the same line 
of channel. In this way it is obvious that not only will 
the advantage of a permanent navigable track be obtained, 
but the constant action of the currents of flood and ebb 
tide flowing in the same channel, will secure a much 
greater permanent depth than they could possibly do if 
permitted to wander at random through the estuary. 



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186 ISLA2n> NAVIGATION. 

Bometimes operating in the same channel, and at other 
times directly opposed to each other, and these results 
can best be attained by training walls. 

In 1836, Mr. James Walker was, I believe, the first to 
propose low parallel walb for the Clyde at Dumbarton ; 
but I believe I am also correct in saying that the Eibble 
was the first river, passing through an estuary of sand- 
banks, which was improved by excavation and low training 
walls ahne ; and even long subsequent to the successfiil 
construction of training walls on the Kibble, jetties con- 
tinued to be erected on the Tyne, the Tees, and other 
rivers. Even in 1850, twelve years after the Kibble 
works were commenced, I gave evidence in support of a 
Conservancy Bill £3r the river Tyne, which was intended to 
introduce a new system of treating the river ; and in speak- 
ing of the condition of the Tyne at that time, I stated that 
" the works which have been executed to improve its condi- . 
tion, consisting of groynes or jetties rtueed above the level 
of high-water mark, and extending into the channel, are 
by no means judicious ; that had such works berai adopted 
as have of late yeaia been introduced with unquestion- 
able advantage in various rivers, Hie Tyne would, like 
them, have been in a condition very different &om what 
it now preefflits ; and moreover, by the present system of 
working, I believe, that the Tyne, viewed as a whole, 
never can be improved to any great extent, if at alL" I 
need not add that these remarks in no respect apply to 
the present state of the Tyne navigation. 

The proposal to improve the river Kibble l^ boldly 
projecting rubble waUs through its sandy estuary, with- 



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TWAL COHPABTHENT. 187 

out any cross jetties to check ihe tide and preyent its 
flowing up on either side behind the walls, was con- 
sidered aB hopeless, and it was with no little difficulty 
the directors of the Company, amid much contendiog 
local advice, could be persuaded to try the experiment ; 
and it was not until after several interviews that the 
Admiralty, represented by Admiral Sir F. Beaufort, as 
hydrographer, and Captain Washington, as chief officer 
in the hydrographic department, gave the official assent 
to works which hare since, in many instances, proved to 
he the proper treatment for such a river. 

Questions hare been raised aa to the comparative compmUn 



cases, the direction of such walls must be determined, not 
by any abstract consideration as to the superiority of 
straight or curved walls, but chiefly by the relative posi- 
tions of the points between which the stream is to be 
conducted, and the outline and geolc^;ical formation of 
the shores and banks of the estuary that intervene 
between those pconts. The consideration of such matters 
may render it ezpedi^it, according to l^e special circum- 
stances of the locaHty, to adopt walls having concave, 
straight, or convex outlines, aa shown in flga. 33, 34, and 
35. 

"Viewed as a purely abetiact question, it may, I think, 
be safely afBnned that a stream is most likely to fiillow a 
permanent course when directed by a concave wall, as 
shown in fig. 33, in which the axis of the stream is repre- 
sented by the dotted line. Dr. Young observes that the 



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188 INLAND NAVIGATION. 

centri&gal force in ciirved cbannels has a tendency to 
draw the greater portion of the water to the concave Bide, 
and thus the greatest scouring power, and consequently 
the greatest depth of the stream, will be found upon that 
side, as must have been observed by all who have had 
occasion to study Hie subject. In a channel directed by 
straight walls (fig. 34), the current has no such decided 
bias for either wall, and is consequently more easily 
thrown across from side to side. A wall, on the other 
hand, having a convex outline, as shown in fig. 35, is 



'"iJ^t" 




^^^^^^ 




Fig. 33. 




,.**'" ..---"'"""* 




Fro. 84. 




•'*»* 



(especially if the radius of curvature be small) still less 
suitable as a guide, as the line of wall diverges from the 
direction of the axis of the current. These remarks are 
not hypothetical, as I have found that their correctness 
has been verified by cases in actual practice. There is 
doubtless some disadvantage in the deep water being on 
one side of the channel, as shown in the cross section, 
fig. 36. It would be more convenient for navigation were 
the deep water in the centre ; but it is found that the 
current has a tend^icy to adhere to one or other of the 



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TIDAL COMPARTMENT. 189 

walla, and it is better that the channel should keep con- 
stantly to one wall, than that it should alternate firom 
side to side, as is more apt to be the case in absolutely 
straight channels. It is, however, proper to state that 
Mr. Fowler, the engineer of the Tees Navigation, has 
found no practical difficulty in maintaining very constantly 



Fid. 36. 
a &ir navigable channel in the long straight reach on the 
Tees, upwards of a mile in length, where the river is 
trained by two parallel walls. 

The direction of river walls must, however, be carefully 
considered by the engineer with ref^^nce to existing cir- 
cumstances, as it is a point which clearly requires that 
every case be ju(lged on its own merits. But I think it 
will be found safe in executing such works to adhere aa 
closely as possible to the following general rules, which 
are the result of experience : — 

First, The channel through open estuaries should, in 
all caaea where fiinds will admit of it, be guided by double 
walla In cases, however, where the estuaiy is bounded 
by a hard beach, presenting a &vourabte line of direction, 
a single wall may occasionally be fotmd sufficient. All 
curves which it may be necessaiy to introduce should be 
of as large a radius as possible, and should, if practicable, 
be tangential to each other, or to the straight parts of the 
line with which they are connected. 

Second, The walls should not be raised to a higher 
level above the low-water line than is absolutely neces- 



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INLAKD NAVIGATION. 



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TIDAL COMPABTMENT. 191 

saiy for the purpose of conducting tlie early and late 
currenta of the tide; and thar direction should be marked 
by occasional perches. 

Fig. 37 represents the disposition of such walls in 
estuaries, as executed under the direction of Messrs. 
SteTenson. They are raised from 3 to 5 feet above the 
low-water line, so that, while they guide the low-water 
channel, they do not prevent the tide at high water firom 
flowing on either side of them and filling the estuary. 

Third, River walls should, during thar erection, be 
pushed forward with vigour, and not in a desultory, timid 
manner ; the effect of such a course being to increase the 
depth of water in which the wall has to be made, and 
the amount of stone required for its construction. 

Fottrth, It will be found that such walla as I have 
been describing will be most advantageoimly formed of 
rough rubble stones, backed with clay and gravel, in the 
manner shown m fig. 38. 

Fifth, In determining the proper width of channel to 
be formed by training walls, the engineer must be guided 
by a carefiil consideration of the fresh-water and tidal 
dischai^e, and the trade to be provided for. The walls 
on the lower part of the Eibble and the Tees are from 
400 to 500 feet apart. 



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192 INLAND NAVIGATION. 

Care muat be taken not toadoptacKatmelof too great 
width, so as to decrease too much the scouring power 
of the currents. It was found on the Dee, &om a series 
of observations kept for eight years, that the two places, at 
which the depth was most firequently below the standard 
of 15 feet at high water, were Saltucy, where the channel 
had been increased in width to acconmiodate shipping, 
and Upper Feny, where it had been enlaiged to suit the 
feny traffic. Out of 139 instances of deficient depth in 
the river, during the eight years, 65 had occurred at Upper 
Feny and 38 at Saltney. It was found at Saltney that 
the vessels moored at Saltney wharves had the effect of 
increasing the scour on the bottom, and keeping the 
deep water close to the line of quays. An interesting 
result of the eight years' observations was, that the navi- 
gation between Chester and Connah's Quay, on the whole, 
was deepest in February after the winter floods, and 
shallowest in September and October, which accords 
pretty much with my experience of similar riv^*s, and 
will, I believe, be fotmd to be oi general appUccUvm to all 
British rivers. 

It was foimd by Mr. Park, under whose immediate 
directions, as local engineer, the waUs on the river 
nibble were constructed, that their foundations, with few 
exceptions, did not sink more than a few feet below the 
sand, which I have also found to be the case in many 
other places where such walls have been formed in sandy 
bottoms. The fact of their beiog parallel to the tidal cur- 
rents, and of low level, prevents any very severe scour 
from affecting their foundations, as the water, so soon as 



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TIDAl, COMPABTMENT. 193 

it ovOTtope the wall, gets relief by flowing over their 
baabs on either side of the channel ; but notwithBtanding 
this flow of the current ov^ the walk, the track between 
them, being the deepeet part of the river, will be found 
always to afford the best navigable current, so that in 
navigating the channel there is no tendencrf for yesaela to 
be sent across the walla ; indeed, I am not aware of a 
angle instance of ships fouling low training walls. In 
designing walls for the lower part of the Dee, at Connah's 
Quay, Telford, with a view, no doubt, chiefly to mftTfing 
land, advised the Kiver Dee Land Company to make 
their bank much too higK &^d combined with it the old 
transverse jetties. The wall at Connah's Quay is carried 
up nearly to high-water level, and the scour was so great 
that an unnecessarily large amount of stones was ex- 
pended in filling up the deep pools scoured below the 
level of the sand. In deigning improvements for the 
Dee Navigation, in 1840, I recommended that the high- 
level walls shotdd be discontinued, and that a wall on 
a low level should be adopted, Edmilar to the works 
executed on the Eibble, where considerable difficulty was 
encountered in introducing the low parallel walls, as ex- 
plained at page 186. In forming these walls it will be 
found necessary &om time to time to add additional 
stones to make up slips, before attempting to pitch t^e 
top or fece of the waU. 

3. CUmng Stfimdiary Ghanneia. 
The next work to be noticed is the closing of what I 
term Bubffldiary channels, which are sometimes called 



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194 INLAMD NAVIGATION. 

back laixs or blind channels, and are caused by islands in 
the river, so tliat instead of flowing in one broad, deep, 
and navigable bed, kept open by the whole available 
scouring power, the river is divided into two shallow 
channels, neither of them affording a good navigation, 
while frequently a ford or shallow is deposited both 
above and below the island caused by the disturbance 
which occurs at the jtmction of the divided currents. 
The object of these operations will be understood from 
. 39, which shows a portion of the Tay. On the Tay 




and the Lune several such secondary branches were, with 
much advantage to the navigation, closed up by means of 
embankments, formed of gravel dredged fixjm the river, 
while the other or principal branch was enlarged and 
deepened, so as frdly to compensate for the closing of the 
smaller channel, and assimilate its cross-sectional area to 
the rest of the navigable track. 

The closing of the streams behind the islands on the 
Tay, and turning the whole flow into one channel, was 



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TIDAL COMPABTHENT. 195 

not followed hy a sens&le rise in the Emr&ce or ^flooding 
of the i^wres in the augmented state of the river. But 
there could he no doubt as to the increase of its velocity, 
which was very marked. For some time, indeed, it was 
found that every flood wasted and cut the banks to such 
an extent as rendered it imposmble to draw the fishing- 
nets imtil the sectional area had been enlarged, and 
the current so reduced as to admit of the banks being 
properly dreased and laid with broken stone, showing 
that there may not be any sensible increase of height 
in the sui&ce, even when there is a considerable aug- 
mentation in the quantity of water discharged ; but see- 
ing that the increased velocity Is due to increased slope, 
there must have been some elevation of the sur&ce 
oppoeite to the closed entrance, so that it is not possible, 
as averred by certain philosophers of the Italian school, 
that a amaJd river may enter a large one without increas- 
ing its sectional area.' The shutting up of all such lateral 
branches should invariably be preceded by a careful com- 
parison of accurate sections of the two channels and the 
velocities of the currents running in them. 

The embankments as shown in fig. 39 should be made 
at the upper end of the channel to be closed. They 
should be raised gradually across its whole width. They 
may be made of &scines or pile-work, whm iJie bed is 
soft, and in cases where die dredgings from the river 
consist of heavy gravel, I have made banks by simply 
depositing the dredged materials across the mouth of the 
channel, allowing the currents to scatter them to the 

' See Friii's MrnHka on thii (xmtrOTBny, p. 61. 



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196 INLAND NAVIQATION. 

proper dope. Dredgings so deposited fix)iii day to day 
will ultimately bring the bank to its proper height, when 
it can be further strengthened fi*om behind, by floating 
the punts at high water up the old channel, which may 
be left open at the lower end so as to allow it to silt up. 

4. Substituting Straight CtUs/or Bends. 
ti riTera which follow a tortuous course navigation is 
sometimes greatly impeded by the abruptness of the 
bends, and the difficulty of navigating a ship through 
them, and where practicable it is sometimes desirable to 
obviate this by forming straight cuts. This is an opera^ 
tion, however, that must not be entered on without care- 
ful study of the tides and due consideration of the effect 
of the altered slope and currents on the river's bottom 
above and below the site of the cut. The levels should 
also be accurately determined and considered, as it may 
happen that the substitution of a straight cut for a long 
detour may involve a rate of inclination so steep -as to 
induce currents injurious to the bed and banks of the 
river, and inconveniently rapid for navigation. Cuts 
have been formed with great advantage on some rivers, 
and I may particularly mention the Tees as a case where 
they have been successfully adopted. The Maudale Cut 
near Stockton was made, in 1810, and by a short coiurse 
of 220 yards it cuts off a detour of nearly 2J miles, the 
navigation of which was exceedingly intricate. A second 
cut of 1100 yards in length was made on the Tees, in 
1830, to cut off the Portrack bend, another inconvenient 
detour in the river's course. 



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TIDAL COMPABTMENT. 197 

Probably the largest artificial water-channel that haa 
been executed, is that for the diveraon of the river Dee 
at Aberdeen, for the particulars of which I am indebted 
to Mr. W. D. Cay, engineer to the Aberdeen Harbour 
Trustees. He Harbour Truatees, in the year 1868, ob- 
tained Parliamentary powers to div^t the river, and to 
reclaim an area of knd amounting to about 120 acres. Of 
this area it is intended to reserve a portion as water space 
to serve in the meantime as a tidal basin, and subsequently, 
when required, to be formed into a dock. The remainder 
will be embanked and formed into quays and streets, and 
partly feued for public works. The length of the new 
channel is 2000 yards, that of the old course being 2500 
yard& The bottom is excavated to a tmiform slope of 



Fig. 40. 



^^^ 



I in 1300 downwards towards the sea, being parallel to the 
expected highest flood-line. The width of the channel at 
the bottom, as shown in fig. 40, is 170 feet ; the bank on 
the north side has a slope of 3 to 1, and is protected with 
piles, day, and stonework ; on the south side the slope 
has an inclination of 10 to 1, this fiat slope being arranged 
for the convCTiience of the salmon-fishings. The tops of 
the banks are 25 feet above the bottom of the channel, 
and the width at the level of the top of the banks is 495 
feet. The bottom of the channel at the upper end is 2 
feet, and at the lower end 6 feet below low water of ordi- 
nary spring-tides; high water of the same tide rises 12 
feet 9 inches above the low-water level 



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198 INLAND NAVIGATION. 

The amount of excavatioQ of the new channel was 
about 1,036,000 cubic yards ; about 916,000 cubic yards 
were taken out dry by mft-tnial labour, and drawn out in 
waggons, the remainder, — 120,000 cubic yards, — being 
dredged. 

5. Dredging. 

The introduction of even the simplest of mechanical 
appliances for excavating materials under watw, raising 
them to the surface, and depositing them in barges, waa 
an important era in canal and river engineering. The 
first employment of machinery to effect this object is, 
curiously enough, like the discovery of the canal lock, 
cMmed alike for Holland and Italy, in both of which 
countries dredging is believed to have been practised be- 
fore it was introduced into Britain, and the moving power 
at £rst employed waa, it need hardly be said, manual labour. 
1 The Dutch, at a very early period, employed what is 
termed the " bag and spoon " dredge for deaning their 
canals. It was simply a ring of iron, about 2 feet in 
diameter, flattened and steeled for about ooe-thiid of its 
circmnf^rence, having a bag of strong leather attached to 
it by leathern thongs. The ring and bag were £zed to a 
long pole, which, on being used, was lowered to the 
bottom from the end of a barge moored in the canal or 
river, A rope made fast to the iron ring was then wound 
up by a windlass placed at the other end of the baige, 
and the spoon was thus dragged along the bottom, and 
was guided in its progress by a man who held the pole. 
When the spoon reached the end of the barge where the 
windlass was placed, the winding waa still continued, and 



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TIDAL OOMPABTMBNT. 199 

the suspending rope being nearly perpendicular, the bcig 
was raised to the aux&ce, bringing with it the stuff exc^ 
vated while it was being drawn along the bottonL The 
windlass being still wrought, the whole was raised to the 
gunwale of the barge, and the bag being emptied, was 
again hauled back to the opposite end of the barge, and 
lowered for another supply. This system is slow, and 
only adapted to a limited depth of water and a soft 
bottom. It has, however, been generally employed in 
canals, and much used in the Thames and at the Foss Dyke, 




owing to want of space and other peculiarities. I found 
it oovid be usefully employed when the steam-dredge, 
though built expressly to suit the contracted limits within 
which it had to work, could not be used. The quantity 
raised at the Foss Dyke, by manual labour, in this way, 
was about 135,000 tons, and the cost did not exceed T^d. 
per ton. Fig. 41 shows the manner in which the bag and 
spoon were employed. 

Another plan, practised at an early period in rivers of Dndgiiigi); ' 
considerable breadth, was to moor two large barges, onetweBniiro 
on either side ; between them was slimg an iron dredging 
bucket, which was attached to both bai^;es by chains 



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200 INLAND NAVIGATION. 

wound round the barrels of crab-wlnclies worked by six 
men in the one barge, and a simple windlaBS, worked by 
two men, in the other. The bucket being lowered at the 
side of the barge carrying the windlass, was drawn by the 
crab-winch on the other barge across the bottom and up 
a sloping platform, which was lowered to the bed of the 
river, and was ultimately emptied in the barge. It was 
again lowered, and hauled across by the opposite wind- 
lass for a repetition of the process. This plan of dredg- 
ing was adopted in the Tay till 1833, and fig. 42 will 



give a pretty good idea of the manner in which the 
apparatus was worked. The dredging-^>oon is shown on 
a large scale at the foot of the cut. 

These early efforts, as perhaps they may be called, at 
dredging, are, I think, worthy of being recorded, and will 
be iuterefiting as compared with the more perfect machi- 
nery used in the present day, some of which I shall have 
to notice. 

In all large operations, these and other primitive ap- 
pliances have now, as is well known, been almost super- 
seded l^ the steam dredge, which was first employed, it is 
beUeved, in deepening the Wear, at Sunderknd, about t^e 
year 1796. The Sunderland machine was made for Mr. 



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TIDAL COMPAETMENT, 



GrimshawlryBoiilton and Watt.' EecM.ving improvements 
from Mr. Hughes, Mr. Bennie, Mr. Jessop, and others, 
the steam dredge, as now generally constructed, is a most 
power&l madiine in skilful hands, excavating and raising 
materials from the depths of 15 to 30 feet of water, ac- 
cording to the size of the machinery, at a cost not very 
different from, and in some cases even less than, that at 
which the same work could be performed on dry land. 

As to the nature and extent of work that may be 
accomplished by dredging, I may state, generally, that 
almost all materials, excepting soHd rock or very large 
boulders, may be dredged with ease. Loose gravel is 
probably the most fevourable material to work in ; but a 
powerfiil dredge will readily break, up and raise indurated 
beds of gravel, clay, and boulders, and even find ita way 
through the sur&ce of soft rock, though it will not pene- 
trate very &r into it. In such cases it is usual to alter- 
nate on the " bucket-frame " a bucket of sheet-iron, for 
raising the stuff, with a rake or pronged instrument for 
disturbing the bottom. 

Hand dredges have been used by Messra D. and T. H.nddnid«B«. 
Stevenson at several placra, by means of which even dis- 
integrated or rotten rock has, at least to a limited depth, 
been raised ; and I believe that in very miany cases the 
sur&ces of submeiged rocks may, by means of such 
machines, be to a small extent broken up and removed, so 
as to obtain in certain situations a considerable increase of 
depth, without recourse to cofferdams, which involve 

^ Snegeioptedia q/" Civil B*gimtriitg, by Edward Cieny , London, 1847; " The 
Dradfpng Uftchjiiw," W«*le'« QuarUr^ Papen, Part L, Londoo, 1843 ; TMe Jm- 
U<ifthe Port of London; hj B. Dodd, EngiDcw, 17S8. 



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202 INLAND NAVIOATION. 

great expense, as well as interruption to the tra£Ba These 
small dredges are worked hj seven or twelve men, and 
cost about £230 to £390. They can work in a depth of 
about 16 feet, and can raise ordinary deposit at a cost of 
Is. 6d. to 28. per ton. 

The construction of large river steam-dredges ia now 
carried on by many engineering firms, each one naturally 
advocating his own arrangement of parte, and consequent 
superiority of performance. 
!>e For details as to the amoimt and cost of work done 
on a river where much dredging is annually performed, I 
perhaps cannot do better ihan. refer to tiie Clyde, for in 
no river has dredging been more extensively or success- 
fully employed. I am indebted to the kindness of Mr. 
James Deas, the engineer to the Trustees of the Clyde 
Navigation, for the following information regarding the 
apparatus employed, and the extent and cost of the work 
done, which will be found both interesting and valuable. 

Mr. Deas says truly that the Clyde Trustees employ 
probably the largest dredging fleet of any trust in the king- 
dom, in TTi fti n t-^'TJiTig and still deepening and widening the 
river, to meet the ever increasing demands of the shipping 
trade. 

Last year 904,104 cubic yards, or about 1,130,000 
tons, were dredged fivm the river, of which 689,560 cubic 
yards were carried to sea by steam hopper barges, and 
214,544 cubic yards deposited on land by means of punts. 
Of this 904,104 cubic yards, 345,209 cubic yards were de- 
posit from the higher reaches of the river and ite tribu- 
taries, and &om the city sewers, and 558,895 cuHc yards 



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TIDAL OOHPAKTHENT. 



new material. The tFotal cost for dredging and depositing 
was £35,448, or about 9 '41 pence per cubic yard. 

Owing to the difference in power of the dredging 
machines employed, and the character of the material 
lifted, the cost of dredging varies mucL Last year the 
meet powerful machine, working 2420 houra, lifted 430,240 
cubic yards of sUt and sand, at a cost of 2*60 pence per 
yard, and this was deposited in Loch Long, 27 mUes from 
Glaflgow, by steam hopper barges, at 5 "46 pence pra: yard. 
On the other hand, another dredger working 2605 hours, 
lifted only 26,720 cubic yards of hard gravel and boulder 
clay, at the cost of 20*8 pence per cubic yard, which was 
deposited on the alveus of the river, at the cost of 17'46 
pence per cubic yard; another, working 1831^ hours, 
hfted 122,664 cubic yards of silt, sand, and sewage 
deposit, at the cost of 5*67 pence per cubic yard, which 
was deposited on land at the cost of 16'40 pence per 
cubic yard; and another, working 2233 hours, lifted 
65,160 cubic yards of till, gravel, and sand, at the cost of 
5 '8 9 pence per cubic yard, which was deposited on the 
alveus of the river at the cost of 9"83 pence per cubic 
yBrd. 

The total quantity dredged from the river during the 
last twenty-seven years amounts to 13,617,000 cubic 
yards, or upwards of 17,000,000 tona 

The dredging plant of the Trustees comprises 6 steam 
dredgers, 14 steam hopper bargee, 1 tug steamer, 3 
diving-bells, 270 pimts, and numerous row boats. The 
expenditure for wages of crews, coal, and stores, amounted 
last year to iully £14,000, and for repairs £10,775. 



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204 INLAND NAVIGATION. 

The value of the dredging {Jaut employed is about 
;ei40,000. 

Mr. Deas has also kindly fumished the following 
tables, from which the reader will see the gradual increase 
that has been made on the size of the dredging machines 
to meet the increased depth of water and growing neces- 
Edty of increased accommodation for the larger class of 
vessels which now frequent the river : — 





General Dimensions 


OF 


Dredgers Emplotid on the 


Clyde in 1873. 


Hd. 


Ybu 


Linglh. 


Bnullll 


IWh. 


B.P. 


depth cu 




BtmtAa. 




1861 


FLIn. 
9BS 


Ft to. 
32 4 


Ptin. 

10 


40 


% 


DoDbk 


Punt Loading Machine. 




1841 


95 6 


22 6 


10 4 


24 


18 


Single 


Do. Do. 




ISfifi 


1210 


33 6 


10 


40 


26 


Double 


Hopper Barge Do. 




I860 


108 6 


23 6 


9 


211 


25 


SiDgle 


Pont Do. 




1866 


1610 


29 


10 


7a 


28 


Do. 


Hosier Barge Do. 




1871 


1610 


29 


10 


76 


30 


Do. 


Do. Do. 



No. 8 Dredger — 
Length, 161 feet. 
Breadth, monlded, 29 feet. 
Depth, 10 feet 
Eogiae, 75 horse power. 

Cylinder, 48 inchea diameter. 
Stroke, 3 feet 
One bucket ladder, 90 feet 9 loches between centres. 
Size of buckets, 3 feet 3 inchea X 2 feet 6 inches X 1 foot 1 1 

inches. 
When working in sand, can lift 190 cubic yards per hour. 
Greatest depth can dredge in, 28 feet. 
Working draught, 6 to 7 feet 

Wages, per day of 10 hours — Master, 7b. ; mate, 3s. 9d. ; engi- 
neer, 6b. 8d. ; firemen, 3b. 8d. ; assistant do. and cook, 
3s. 4d. ; bow crabman, 3s. 4d. ; stem do., Ss. id. ; deck 
hands, Uiree at Ss. 2d., one at 3s. ; watchman, 3b. 



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TIDAL COUPABTUENT. 205 

Coals, per day of 10 honn, 65 cwta. 
Tallov, „ „ 2 lbs. 

Oa(Urd), „ „ 16 gills. 

Waste, „ „ IJ lbs. 

St^per Sarge — 
Length, 145 feet. 
Breadth, moulded, 26 feet 
Deptii, 1 1 feet 9 inches. 
Engines, 40 horse pover. 
Dran^t, light (average), 6 feet 6 inches. 

„ loaded, 11 feet. 
Speed, 8 to 9 miles per honr. 
Gai^, 320*cabic yards, or say 400 tons. 
Average distance run, loaded, 20 ndles, 
W^es, per day — Master, 7b. ; mate, 4b. 6d. ; engineer, 53. lOd. ; 

fireman, Ss. 6d. ; deck hands, three at 3b. 4d. 
Coals, per day of 10 hottrs, 70 cwts. 
TaUow, „ „ 5 lbs. 

Oil, „ „ 20 gills. 

Waste, „ „ 2 lbs. 

Quantity and cost of dred^ng done by No. 8 Dredger during year 
ending 30th June 1871 :— 

Wages, £678 

Coals, . . ' 371 18 3 

Stores, 182 7 1 

£1232 6 4 

Bepaire, 1669 6 11 

£2901 12 3 
Interest and depreciation — 

Cost of dredger, £17,663, at 10 per cent., 1765 6 

£4666 18 3 



Time irorked daring year, S419f engine-honrs. 
Sand, Bilt, till, and gravel litied, 430,240 oabic yardB. 

177-80 cubic yards lifted per hour, 
2'60 pence cost per cubic yard lifted. 



24,1931 hoars, 

£4666 18 3 
430,240 cubic yards, 



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206 



INLAND NAVIGATION. 



Quantity and coat of conveying and diecharging the total dredgjngs liftnd 
by Nob. 6 and 8 Dredgers during the year ending 30th Jnne 1871 — 
Wages, coals, and stores, £6917 6 
Bapurs, . . . 3265 7 9 

£10,172 8 2 

Interest and de|N-eciatJon— 



Cost of 10 Hopper Barges, £51,610, at 
10 per cent., .... 



5151 



£15,323 8 2 



5'46 pence cost per cnbic yard. 
" total dred^gs conveyed. 



673,240 cubic yardfl, " 
JVbfe. — Four Hopper barges are required to keej^ one dredger in 
constant work. 



Abstract of the Quantity and Cost per cubic yard of Dredging and 
Depositing during the year ending 30th June 1871. 



Dredssr.rto. 


Natara of itnlT, 
and wbcrc 
d»dg»l 


! 
II 
1 


11 
is. 


PmnperciibEcTaM. 


f 


III 


1 


lO-OO" 


II 

Ii'62 


Total 
22-07 


No. 1 Dredger, 


8Md,dll,a*d 

BBW^^ from 


m,m 


68-06 


6-67 




2-8fl 




























































Ho. 6 Da 


Hanltm,gra- 

fivm Enkine 
Finy, etc. 
Sand, cUt, and 
mud,fromPt 


66,1«) 


2»-18 


689 


... 


1-76 


6-42t 


^-65 


i&n 


So.e Do. 




SS'IS 


»-S6 


K-«) 






























Ola^w, etc. 




















clay from Kr- 
ikine Ferry, 


l«,7!«l 


10-26 






S-34 


G-421 


970 


as-w 










































and BowUng 


480,2*0 


177-80 


a-60 


6-*6 






... 


s-oe 


10 Hopper 










'T^ 










T^rssm., 












■1^ 









Noa. 1, C, and 7 at« poat-loadiiig machiDea. tfoa. 6 and B an hopper beige matdiioea. 

• Contncl<ir'ipTl»fuTdlachaigIqgatBliaisnroodFark,fiuihMl<«i>HpdK)ti,aad«WMfi^ a 
1 DUdiiiHliis by Traateet" men <m riTM Unka MM liikliw Fany, bj S«isMiii;p»ii«iiiiid irtl«I(iie. 



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TIDAL OOHPAATUEMT. 



207 



Mr. Murray lias given me the following tabxdar view i>«agin([«i 
of the dredging of the Wear at Sunderland, which is also 
an interesting record of the quantity and cost of material 
raised by a dredging machine ; but this view is not givrai 
by way of compariBon with the preceding, as there is no 
analc^ between the cases. The contracted state of the 
Clyde, the frequent iatemiptious to which the work was 
subject by the constant passage of vessels, the expense of 
r^noving and depositing the stuff, and the higher rate of 
wages, must necessarily have increased the cost of exe- 
cuting the work ia that situation. 

Tabulab View of the DasDaDiQ of the Wear at Sunderland 
JS 1842-46. 



tata. 


Totil 




pSSL 


forRepnIn 
pwinimm. 


perHmoiB. 


Total 


Anmga 


IS42 
1843 
1844 
1845 
1846 


128,246 
141,826 
90,980 
101,076 
140,300 


922 1 2 
87916 
6671* 4 
721 
724 S 4 


i 1. d. 

Ill 

70 
as 59 
66 7 « 
68 2 6 


£ (. It 

7S4I6 
603 13 4 
2«» 2 1 
336 8 
600 17 2 


704 17 n 
780 13 11 
663 9 10 
627. 7 10 
620 3 2 


2492 10 I 
2240 8 8 
1466 11 
1661 12 4 
1803 8 1 


4-0S6 
8-804 
3-842 
8-921 
3-063 


1842 

to 
1846 


Heoca tbe &Tenge cort per ton od fira ysHa 
For nkmg ud depodtiiig at ■«, . 
For fuel, .... 
For labooT in repsin. 


irork- 




-1-628 
=0149 
-0-943 
-1-243 








At 


nge total 


Expenditn 


t*. 






-.3-863 



This is perhaps the best place to mention some im- impraremeiita 
provements that have been suggested on the present, or dredgas. 
I may, I suppose, term it the old, style of dredge, and the 
first that I shall mention is that of Messrs. Simons and 
Company, London Works, Renfrew, who have had very 



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208 INLAND NAVIOATION. . 

large experience in the construction of dredging apparatus. 
They have patented and constructed what they have 
called a hopper-dredge, combining in iteelf the advantages 
of a dredge for raising the material, and a screw hopper 
vessel for conveying it to the place of diachai^, both of 
which aervices are performed by the same engines and the 
same crew. In contracted rivers and exposed bars and 
channels, the convenience of dispensing with hopper-punts 
lying alongside and chafing a large unwieldy dredge, 
must on some occasions be desirable, and the arrangement 
also secures the advantage of delivering the stuff at the 
level of a few feet above the deck, thus avoiding the long 
bucket-ladder and high level of discharge required for 
delivering into punts or barges, moored alongside the 
dredge. But the chief advantage which ihe patentees 
claim is a considerable saving of expense, not only in 
dred^ng, but in depositing the stuff at a distant point, 
such as Loch Long in the Clyde, and, if this saving can 
be satisfectorily established, there is much to commend 
the use of such craft as they have patented, especially in 
a crowded navigation. 

Another of the recently suggested Improvements is 
that by Mr. C. Bandolph, who, in 1870, proposed that 
instead of the ordinary dredging-buckets, pipes should be 
lowered until they came into contact with the sand or 
mud at the bottom. The tops of these pipes were to be 
in communication with powerM centri&gal pumps, so 
that the velocity of the inflowing water through the pipes 
coidd be made so great as to cany with it a large per- 
centage of the sand or mud from the bottom, and when 



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TIDAL OOMPABTMENT. 209 

the solid matter, and the water in which it is suspended, 
were raised to the desired height, they would flow freely 
to any required place for deposit of the suspended material 
Mr. Thomas Stevenson, in his book on Harbours,' states 
that Mr. Duncan, the late engineer of the Clyde Navi- 
gation, had given ^>im an extract from a report by M Le 
Ferme, dated 30th September 1859, on the result of a sUt 
pump of 20 horse-power, sunk 18 inches into the mud, 
proposed by M. Cache at St. Nazarie, whic^ did its work 
effectively. 

Another arrangement is that of raising the material Draagii««t 
by buckets in the ordinary way, and thereafter receiving sne* ouuJi. 
it in a vessel and floating it off by pipes to tiie place of 
deposit. This of course can only be done where the place 
of deposit is close to the spot whence iixe material is 
dredged. Two pluis have berai proposed for effecting 
this. One of these has been used on the Amsterdam 
Canal, where the stuff is discharged from the buckets into 
a vertical cylinder, and is there mingled with water by a 
revolving Woodford-pump, and sent off under pressure 
to the place of deposit ia a semi-fluid state. At the Am- 
sterdam Canal this was done by pipes made of timber, and 
hooped with iron like barrela These wooden cylindOTs 
were made in lengths of about 15 feet, connected with 
leather joints, and floated on the sur&ce of the water, con- 
veying the stuff to the requisite distance, Uke- the hose 
of a fire engine, under a head of pressure, I believe, of 4 
or 5 feet, and depositing it over tfae banks of the canaL 
A somewhat ^milar process was used on the Suez Canal, 

' The ConttmeHon of Haihi)ikt\ by T. StoToiuoii, Oiril En^eer. 



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210 INLAND NAVIGATION. 

not, howevOT, by using pumps, but simply by rmming 
the stuff to the banks on steeply inclined shoots, which 
were supplied with water when the material r^sed did 
not contain sufficient water to cause it to run freely. 
Another pl^i is that on which Mesera Simons and Com- 
pany are now constructing a dredge for E^ypt, in which 
the stuff is to be propelled by jet-pumps, forcing a power- 
ful stream of water through the discharge pipes. The 
dredgings will be conveyed by this means for a distance 
of two or three himdred feet on either side of the dredger, 
and at a considerable elevation. 

It is obvious, however, that these arrangements can 
only be applied in situations where the material to be ex- 
cavated is not of a hard nature, and where the place of 
deposit is close at hand. I can conceive, for example, in 
keeping clear the Suez Canal, that such appliances may 
be very useful, as the soft deposit of the canal has only to 
be raised and projected over the banks on either side. 
But this is not the place to discuss the claims of different 
inventors, which pwhaps can only be settled by the actual 
performance of these arrangements when &lly tested by 
practice. Having thus briefly noticed them I shall not 
dwell further on the subject, but conclude with a few 
practical observations on dredging as more immediately 
applicable to the rivers of this country. 
LongHfldhua In river dred^^ two systems are pursued. One plan 

dredgiDs. consists m excavating a series of longitudinal furrows 
parallel to the axis of the stream, the other in dredging 
cross furrow from side to side of the river. It is found 
that inequaUties are left between the longitudinal furrows. 



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TIDAJL COMPAETMENT. 211 

when that system is practised, which do not occtir to the 
same extent in side or cross dredging, and I have invari- 
ably found cross dredg^ to leave the most uniform 
bottom. To explain the difference between the two 
systems of dredging it may be stated, that in either case 
the dredge is moored from the head and stem by chains 
about 250 &thoms in lengtK These chains, in improved 
dredges, are wound round windlaasee worked by the 
engine, so that the vessel can be moved ahead or astern 
by simply throwing them into or out of gear. In longi- 
tudinal dred^ng the vessel is worked forward by the 
head chain while the buckets are at the same time per^ 
fonning the excavation ; so that a longitudinal trench is 
made in the bottom of the river. When the dredge has 
proceeded a certain length, it is stopped and permitted to 
drop down and commence a new longitudinal furrow, 
parallel to the first one. In cross dredging, on Uie 
other hand, the vessel is supplied with two additional 
moorings, one on either side, and these chains are, like 
the head and stem chains, wound round barrels wrought 
by the engine. In commencing to work l^ cross dredg- 
ing, we may suppose the vessel to be at one mde of the 
channel to be excavated. The bucket-fiame is set in 
motion, but instead of the dredge being drawn forward 
by the head chain, she is drawn to the opposite side of 
the river by the side chain, and having reached the 
extent of her work in that direction, she is then drawn 
a few feet &rward by the head chtun, and, the bucket- 
frame heang still in motion, the vessel is hauled back 
again by the opposite chains to the side whence she 



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212 INLAND NAVIGATION. 

started. By means of this transverse motion of the 
dredge a series of cross fiirrows is made ; she takes out 
the whole excavation fixim side to side as she goes on, 
and leaves no protuberances such as are found to exist 
between the fiirrows of longitudinal dredging, even where 
it is executed with great care. The two systems will be 
best explained by reference to fig. 43, where A and B 
are the head and stem moorings, and D and C the aide 



moorings ; the arc e/ represents the course of the vessel 
in cross dredging ; while in longitudinal dredging, as 
already expkined, she is drawn forward towards A, and 
again dropped down to commence a new longitudinal 

fiuTOW. 

Ill some cases, however, the bottom is found to be too 
hard to be dredged until it has been to some extent 
loosenpd and broken up. Thus at Newry, Mr. Eennie, 
after blasting the bottom In a depth of from 6 to 8 feet 
at low water, removed the material by dredging, at an 
expense of from 4s. to 5s. per cubic yard. The same pro- 
cess was adopted by Messrs. Stevenson at the bar of the 
Erne at Ballyshannon, where, in a situation exposed to 
a heavy sea, large quantities of boulder stones were 
blasted, and afterwards raised by a dredger worked by 



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TTOAI- COMPABTMENT. 213 

hand at a cost of about 10s. 6d. per cubic yard. But the 
most extensive application of blasting, preparatory to 
dredging, of which I am aware, was that on the works for 
improTing the Severn, l^ Sir William Cubitt, of which 
an interesting and instructive account is givrai by Mr. 
George Edwards, in a paper addressed to the Institution 
of Civil Engineers, from which the following particulars 
are taken :^ — 

" It appears that a succession of marl beds, varying 
from 100 yards to half a mile in length, were found in the 
channel of the Severn, which proved too haxd for being 
dredged, the whole quantity that could be raised being 
only 50 or 60 tons per day ; while the machinery of the 
dredges employed was constantly giving way. Attempts 
were first made to drive iron rods into the marl bed, and 
to break it up ; a second attempt was made to loosen it 
by drag^;iQg across its sur&ce an instrument like a strong 
plough. But these plans proving uusuccessfid, it was 
determined to blast the whole sur&ce to be operated on. 
The marl was very dense, its weight brang 146 lbs. per 
cubic foot ;^ and it was determined to driU perpendicular 
bores, 6 feet apart, to the depth of 2 feet below the level 
of the bottom to be dredged out -The bores were made 
in the following manner, from floating rafts moored in the 
river ; — ^Kpes of ^inch wrought-iron, 3^ inches diameter, 
were driven a few inches into the marl Through these 
pipes holes were bored, first with a l^inch jmnper, and 
then with an axiger. The holes were bored 2 feet below 

1 "Aeconnt of Bluting on the Sereni," by Qeo^^ Edvards, C.K (JTimfea 
e/Proaedinifiif Irutiiuaonlif Civil Sngineeri, *oL ir. p. 361.) 

' Clay weighs about 109 lb.. Kid lauditone about 16S lb., per cnbtc foot. 



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214 INLAND NAVIGATION. 

the propcBed bottom of the dredging, as it was expected 
that each shot would dislocate or break in pieces a mass 
of marl of a conical form, of which the bore-hole woiold be 
the centre and its bottom the apex ; so that the adjoining 
shots would leave between th^n a pyramidal piece of 
marl where tiie powder would have produced litUe or no 

Watar Level 



efiect By carrying the shot-holes lower than the in- 
tended dredging, the apex only of this pyramid was left 



< * !i il * ! il * !i * I 






to be removed ; and in practice this was found to form 
but a small impediment. Fig. 44 is a section of the bore- 



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TIDAL COUFABTHENT. 215 

boles; and %. 45 a plait, in which the inner dotted 
circles represent the diameters of the broken spaces at 
the level of the bottom of dredging. The cartridges were 
formed la the ordinary way, with canvas, and fired with 
Bickford's ftise. The weight of powder used for bore- 
holes of 4 feet, 4 feet 6 inches, and 5 feet, were reepec- 
tively 2 lbs., 3 lbs., and 4 lbs. The effect of the shot was 
generally to lift the pipes, whidi were secured by ropes 
to the rafts, a few inches. Mr. Edwards says that not 
one in a hundred shots missed fire, and these shots were 
generally saved by the following singular expedient : — ^The 
pointed end of an iron bar, -g-inch diameter, was made 
red-hot, and being put quickly through tbe water, and 
driven through ibe tamping as rapidly as possible, was, in 
nine cases out of ten, sufficiently hot to ignite the gun- 
powder and fire ihe shot. 

" The cost of each shot is calculated as follows : — 



Use of material, .... 

Labour, 

Pitched bag for charge, 

3 Ibe. of powderat 6jd., . 

15 feet of patent fiue at -^ths of a penny, 

Pittdi, tallow, twine, coals, etc, . 






1 


n 








9 








H 



£0 



Cost per ehot, 

Each shot loosened and prepared for dredging about 4 
cuHc yards ; so tbat the cost fer blasting was Is. 9d. per 
yard. The cost of dredging the material, after it bad 
been thus prepared, was 2s, 3d. ; making the whole 
chaige for removing the marl 4s. per cubic yard." 

Mr. J. Coode, in August 1871, made some interesting 
experiments on blasting below water, at St. Heliers, 



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216 INI<AND NAVTOAnON. 

Jersey, the result of which he has kindly communicated 
to me. The object Mr. Coode had in view was to demon- 
strate the feasibility of removing a mass of rock lying 
below low water by means of oompreased gun-cotton, 
without drilling holes for the insertion of the cftarges, as 
in ordinary quarry blasting. 

The rock upon which the trials were made at Jersey 
consisted of a bard syenite, with veins of trap; the 
rock, as a whole, was very compact, but numerous small 
" heads " or joints were interspersed throughout the mass 
— a circimiBtance, doubtless, greatly in fevour of the rend- 
ing or " shivering " action peculiar to gun-cotton in the 
compressed form. 

Tin canisters, containing charges of 5 lbs. aod 10 lbs. 
of compressed gun-cotton were prepared for these trials 
by Messrs. Prentice, of Stowmarket. They were fired 
simultaneously, in sets of three at a time, by means of a 
magneto-electric apparatus. The charges were placed 
upon the surfiice of the rock to be acted upon, and, as feur 
as practicable, in crevices or hoUowa. They were fired at 
such times as to insure a great " head " of water, in order 
to obtain the greatest possible advantage from the down- 
ward action of the explosive compoimd. The results of 
the experiments at St. Heliers led Mr. Coode to believe 
that about 2 tons of the rock below low water at that 
place maybe blasted and rendered in a fit state for lifting 
by each lb. of gun-cotton employed in the manner above 
described. It was, and still is, Mr. Coode'a intuition to 
try the comparative efiect of " licho-fracteur " and gun- 
cotton, but he has hitherto been prevented from doing so 



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TIDAL COMPAllTMENT. 217 

by the sfcrmgency of the " Nitro-Glycerine Act " of 1869, 
which makes it a penal o&nce to import, convey, or 
mauu&cture nitro-glycerine or any of its compounds 
within the United Kingdom, unless by special license 
firom the Secretary of State, but no such license can be at 
present obtained as regards litho-&acteur. 

In some cases dredging has to be conducted inDt«dgingjii 
exposed situations, such as the deepening of the " flats " "nation*, 
at Londonderry and tiie bar at Carlingford. The 
process of dredging at ihe Foyle could not be con- 
ducted when the waves exceeded 2 J feet; and Mr. 
Barton at Dundalk so far confirms this, as he esti- 
mates a swell of 2 feet as the highest to work in. Mr. 
Barton states that the bar at Carlingford, which is 
very exp(»ed, Gonfiists of hard blue day, with a coating 
of large boulders. The dredger employed was built by 
Messrs. Simons and Co. of Ben&ew. She is 157 feet 
in length, 27 feet beam, and 9 feet 6 inches in dept^ 
Her bucket-ladder is 90 feet long, with 42 buckets, and 
she dredges in 35 feet water. She has an en^ne of 50 
horse power, and her work varies firom 100 to 4000 tons 
per day, but her average work is 1000 tons per day, and 
she has brought up with her buckets boulders weighing 
3 tona All stones above that w^ht are removed by 
divers, 

6. Excavation. 
But there are cases where the bottom cannot be 
dredged, and where it is necessary to have recourse to 
other appliances for its removal, such as the diving-bell 



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218 INLAlfD NATIOATIOK. 

y Diring-beii. Or divliig-helmet, and cofferdams. The diving-bell has, 
in conjunction with dredging, been much used on the 
Clyde, and Mr. Bald gives the following account of the 
operation aa conducted on that river : — 

"Between Erskine Ferry and the New Shot Isle 
the bed of the Clyde, for a distaQce of 2000 yards, was 
greatly encumbered with boulders, which were highly 
injurious to vessels if they grounded there; and fre- 
quently large ships, in being tugged through this part 
of the river-channel, had thdr copper bottoms injured 
when they touched the rocky channel-bed. In deepening 
and clearing this part of the river, two diving-bells were 
employed, and one, and sometimes two, steam dredgers. 
The clearing and deepening of this channel was exceed- 
ingly severe on the machinery and working gear of the 
steam dredgers ; the speed of the engines was therefore 
governed by the nature of the material in the bottom, 
and although the iron-work frequently gave way, yet 
spare linlfH and buckets being ^ways ready to replace 
those which broke, there was httle interruption to Uie 
continuous working of the dredgers. When the dredgers 
had cleared away the material which covered the boulders 
in the bottom of the channel, the diving-bell boats were 
worked over the groimd so cleared, removing all the 
larger boulders ; and when that part of the channel had 
been cleared of them, the dredgers went again over tha 
same bottom, removing all the lighter material from the 
heads of the lower boulders, preparatory to the bells com- 
mencing again; and these operations were continued until 
the necessary depth was attained. 



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TIDAL COBIPABTBiENT. 219 

" The buckets of the steam dredgers, in working along 
the bottom, always slipped over the head of the large 
boulders, which the diving-bells alone could lifb aud re- 
move. Some of these masses of trap or whinstone were 
4 and 5 tons in weight, and &om their rounded forms 
and smooth sur&ces, it was evident that they had been 
brought from some distance. Some of them were of 
sandstone, but they were more angular than the trap 
boulders. Quantities of these boulders, lifted from the 
bed of the channel, might be seen lying along the sides of 
the river ; and many of them had since been split and 
broken up by gunpowder for repairing the river dykee. 
The tops of some of the large boulders lifted from 
the bed of the channel were foimd grooved to a depth 
of about an inch or more, by the ships' keels having 
been rubbing over them ; and metallic particles were dis- 
tinctly to be seen upon their surface. In removing these 
boulders from the bed of the channel, the diving-bell men 
fotmd numerous fragments of copper and iron which had 
been torn off the ships' bottoms and keels by the large 
stones ; but latterly this had not been the case, as great 
progress had been made in the removing of the boulders, 
and the deepening of the channel." 

Large isolated masses of stone have also been removed By n>»utian. 
en masse by fixing louisea in iheai, and reusing them by float- 
ation. On the Tay many boulders were raised in this 
manner, one of which weighed upwards of 50 tons. Where 
a large area and considerable depth of sohd rock has to 
be removed, it will generally be found moat advantageous 
to employ cofierdams ; but t^e chief objections to the use 



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220 INLAND NAVIGATION. 

of daiQS in the narro'w chann^ of rivers are the incoo' 
venience they cause to shipping by increaaiDg the cur- 
rents, 80 as to render navigation past them difficult or 
dangerous, and the obstruction they offer to the discharge 
of water when the river is in high flood. An illustration 
of this occurred at the Kibble, near Preston, where a 
solid band of red saudstone, upwards of 300 yards in 
length, crossed the river and restricted the navigation, 
even at hi^est springs, to "lighters" or "flats" of 
small draught ; and, in order to gain tbe requisita depth, 
it was found t^t an excavation of the ma-Timiim depth 
of 13 feet 6 inches must be made through this solid bed 
of rock. It was originally intended to form a temporary 
channel, and to divert the river while the excavation was 
being made, but the rock was &und to extend beyond 
the river's bank, and even to rise in level on the adjoin- 
ing ground, and there seemed to be no other course open 
By coOeidami. but to oiect a coffordam in the navigable channel In 
doing this, however, there were two difGculties to contend 
witii ; for not only had the dam to be fixed on a rocky 
bottom, but the narrovraess of the river, and the necessity 
of preserving a channel for flood-water, and occasional 
passage of a " lighter," left only a very narrow space for 
a foundation on which to construct it. To overcome this 
double object, I designed a coff^'dam, which was found 
to answer the requirements of the case.^ It consisted, as 
shown in fig. 46, of two rows of iron rods, 3 feet apart, 
jiuuped into the rocky bottom, and supporting two 

' " Deicriptiou of • Cofferdam ncUptod to » Hard Bottom," by I>»vid Steven- 
ion, CB. (TVoM.q/'/iMf. o/CWifiiff&Mw*, voLiu.p.377.) 



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TIDAL COMPARTMENT. 






^ 






'~'Xi « 



I ; 



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222 INLAND NAVIGATION. 

linings of planking, tlie intermediate space being filled 
with clay, and the whole structure being stayed fix)m the 
inside, so as to present no obstruction beyond the outer 
line of the dam. Three dams of this construction were 
fonued in the Kibble ; and by means of them a bed of 
rock, 300 yards in length, and of a TnATimnin depth of 13 
feet 6 inches, was successfully excavated. The maximum 
depth of water at high water ag^nst the dam was 16 
feet, but in very high river floods the whole dam was 
sometimes completely submerged ; but on the water sub- 
siding, it was found that the iron rods, on which alone its 
stability depended, although only jumped 15 inches into 
the rock, were not drawn firom their fixtures. On one 
occasion, on visiting the works, I found the river in high 
flood, the dams submerged, not even the tops of the iron 
rods being visible, and a very strong current sweeping 
over them ; but on the water subsiding th^ were found 
to have sustained no damaga This construction of dam 
completely overcomes the difficulty of fixtures in a hard 
bottom, where piles cannot be driven, and offers very 
little obstruction to the navigation. I have used dams 
of the same construction in other works, and have no 
doubt they will be found generally applicable to situa- 
tions where there is a hard bottom and limited space. 

7. Scouring. 
■ The removal of hard portions of the bed of a river by 
dredging or cofferdams, and the direction of the channel 
by low walls, are operatioiM which are in themselves im- 
provements; but they fiirther operate beneficially in 



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TIDAL COMPAKTMENT. 223 

caTisimg the currents to scour the Bofter parta of the 
river's bed. Thus I have found that by dredging a few 
hundred yards of hard material, or erecting a short wall, 
thousands of tons of soft material are scoured away by 
the action of the current alone. In all river improvements 
this is an e£Eect which should be fully taken into considera- 
tion by the engineer, especially in forming estimates ; and 
its importance wUl be apparent on inspecting the section of 
the river Lune (Plate VIII.) By dredging the upper shoals 
of that river, which are marked in hatched lines in the 
section, the whole lower part of the river was deepened 
by the natural scour, without entailing any ^penae in its 
removal To £icilitate Urn scour, a species of harrow has 
sometimes been appUed, which is drawn to and £ro by a 
tug-steamer across the bank to be removed This system 
was extensively employed by Captain Denham in opening 
the Victoria Channel at the Mersey ; it was also employed 
by Messrs. Stevenson at the Tay ; but it is obvious that 
it can only be advantageously used where there is deep 
water in the immediate neighbourhood of the bank to be 
removed, in which the sand and mud disturbed by the 
harrow, and carried o£F by the current, may be depoaited. 
I have found tiat the process of natural scouring has, in 
some situations, continued in operation for many years after 
the completion of the ori^nal work, the low-water level 
of the river continuing gradually to pink ; and, as this 
process goes on, it sometimes happens that hard portions 
of the bottom, originally covered, become gradually ex- 
posed Such obstructions are, in tact, hard portions of 
the bed brotight to light, in consequence of the improve- 



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224 INLAND NAVIGATION. 

ment of the river, and must not be mistaken for accumu- 
lationa due to ill-regulated currents. It is necessary, 
however, that such hard portions should be removed as 
soon as they appear, otherwise they distxirb the currents 
and occasion shoals. "Whenever the depth due to the 
currents acting in their improved direction has been 
reached such obstructions will cease to present them- 



8. Reducing the Indinaiion of the Bed. 
The existence of a not immoderate amount of &11 or 
slope oh the low-water line of a river may always be 
regarded by the engineer as affording good encourager 
ment for its improvement. The slopes of rivers vary 
from a few inches to several feet per mile, as will be seen 
from the tabular list appended to this book, of the phy- 
sical characteristics of rivers in which the inclinations of 
several rivers are given. Du Buat considers 1 in 500,000 
to be the smallest possible rate of inclination that can be 
given to a canal to produce sensible motion. In dealing 
with rivers I should say, from my own experience, that 
the engineer may calculate on reducing the slopes of tided 
navigations to about 3 or i inches per mile, which is equal 
to xiriiTif &"*i t^*t' ^y should not, if possible, exceed 10 
inches per mile, which is equal to a gradient of ■^s'sT'* 
The lowering of the low-water line, and consequent flat- 
tening of the slope or inclination, acts beneficially both 
on the tidal propagation and the scour. As regards 
tidal phenomena it will be found that in all rivers whose 

* The tlopea of " tlie rapid* " immedUtely kbore the Fall* of NUgm are said 



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TIDAL COMPAKTUENT. 225 

bedfl and low-water lines have been lowered, the rate of 
tidal propagation has been increased, and the duration 
of the tide in the river has been prolonged, to the 
benefit of navigation, as will be explained hereafter, when 
we treat of rivers that have been improved. It will also 
be found that the scouring power has in some cases 
been enormously increased, and made to act in the 
most beneficial waj for the chajmel, a result which in 
river engineering can hardly be over-estimated. In 
order to illustrate this it is only necessary to point out 
that the mere cubic contents dredged fixim a ford or 
shoal form no measure of the gain of tidal water due to 
the operation, as explained under "Scouring," because 
the removal of such an obstruction has the effect of 
lowering the low-water line for a certain distance on 
either side of it, and the extent of the lowering will 
obviouBly depend on the ori^nal amount of slope ; if very 
steep the extent will be small, if gentle it will be greater. 
But in either case, whether small or great, the whole of 
the wedge-sloped volumes included between the old and 
new water sur&ces, both above and below the obstacle 
that has been removed, give a clear gain of tide water, 
and the cubic contents of these spaces greatly exceed 
the cubic quantity of material removed fix)m the ford by 
dredging. 

Proceeding on actual calculations of comparative 
sections of the nver Tay, before and after the execution 
of the works, I found that by excavating about 500,000 
cubic yards of gravel the low-water line was lowered so 
much as to admit an additional quantity of ^eo-water. 



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INLAND NAViaATTON. 



amounting on an average to not lesa than one millioa 
cubic yaj^ to be propelled into and again withdrawn 
fit)m tiiat part of the river which lies above Newbm^h, 
during every tide. Thia quantity is equal to nearly two 
hours' discharge of the Tay in its ordinary state, and it, 
therefore, follows that one way at leaat, of representing 
the amount of increase during a year is to compare it to 
two months' constant ordinary flow of the river. 

The velocity of the stream at low water depends 
on the slope, and in our navigable rivers it rarely 
exceeds 3 or 4 miles per hour, and of course is con- 
siderably higher when ihe river is in flood. The tide- 
currente, however, attain a higher velocity than the 
ordinaiy flow of the rivar. But I have found in ahnoet 
every case I have had to investigate that the rate of the 
tide-current was greatly exaggerated. A current of 6 or 
7 knots an hoiu: in the &irway is really hardly navigable. 
Even in the Dee, where the rise of tide is great and the 
currents are very rapid, I do not think they much exceed 
5 mil^ an hour, and ia the Tay above Newbiu^h, and 
riv^^ of that class, where the rise of tide is not so great, 
I do not think the current exceeds 4 miles. A& the 
Severn, agfiin, where there ia a rise of 40 feet of tide, the 
current is said by Captain Beechey to reach 9 nules per 
hour ; at the Mersey, with a very high tide, it was found 
by Captain Denham to run 7 miles ; and Captain Otter, 
in hia survey of the Pentland Firth, gives the velocity off 
the Pentland Skerries at 106 nautical miles per hoin:, 
which I believe to be the highest tide-cunrent ever 
observed. 



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TIDAli OOUFABTHEKT. 



The folloTfring may be taken as the aur&ce velocities 
of the currents in different rivers : — 



Yelocities of the Gdbsents in different Bivers. 



Nuu. 


P«H<mr, 






Mtlai. yda. 






5 


C. EEet. 


Clyde, between Glaagov audi 
junction of Cart, daring ebb, J 


1676 


W.Eald. 


Do., flood, .... 


771 


Do. 


Do., from junction of Cart to ) 
Dumbarton, ebb, . . j 


1 1069 


Do. 


Do., flood, .... 


1561 


Do. 


Do., during high floods below > 


2 1613 


Do. 


Glasgow harbour, ebb, . . [ 


Do. at narrow places during 1 
floods, . . . .j" 


3 1148 

HIIw. 


Do. 


Wear, spring-tide, ebb, . 


llto2J 


J. Murray, C.E. 


Do., neap-tides, „ 


1 toll 


Do. 


Do., flood-tides. 


1 to2 

Knoto. 


Do. 


Tay at Buddonneas, spring-tidw, 


2 to 21 

MIlM. 


North Sea Pflot. 


Do. at Perth, .... 


309 


Messrs. Steyenson. 


Willowgate at Pertih, 


1-55 


Do. 


Dornoch Firth, MeiHeferry, 1 
flood, ]■ 


2-63 


Do. 


Do. do. ebb, 


265 


Do. 


Tay at Mugdnun, flood and ebb, 


2 to 2J 


Do. 


Thames, .... 


2 to2| 


G. Eennie. 



The beneficial effect of the works I have described affect of worki. 
may be summariEed as followB ; — 

First, To depress the level of the low-water line. 

Second, To increase the range of tide. 

Third, To accelerate the propagation of the tide 
through the channel of the river. 



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228 MLAKD NATiaATION. 

Fourth, To prolong the duration of the tide in the 
rivCT. 

Fifih, To equalize the velocity of the tidal currents, 
removing rapids and hores. 

Sixth, To add to the beneficial scoxuing power of the 
river ; and 

Seventh, To increase the navigable depth. 



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CHAPTER IX. 

APPLIC3ATI0N OF THESE WOEK8 DT PRACTICE. 

Ob the River Tfty : deMtiptioD of works exeonted ; alterationB prodaoed on tho 
dopes, and ntea of propftgation and dantion of tidal inflnenoft-i-The River 
Forth : deacription of worka ; their eCFeot on the propagation of the tide — 
Iawi of tidal propagatioa in riven generaUjr — The River Bibble : works exe- 
onted and'their eSecti — The Bivei Lnne : works ezeonted and tiieir effects — 
The River Clyde ; its former and present oondltioii— The Biver Teea : works 
ezecnted and their effects. 

I PROPOSE now, by reference to examples in actual 
practice, to show the beneficial effect produced by the 
works specified in the last chapter, in some navigations 
where they have been adopted, and the first example to 
which, I shall sdlude is the river Tay. The original 
design for its improvement was made by Messrs. Kobert 
and Alan Stevenson, and the works were commenced in 
1833, and afterwards /»rried out partly under my direc- 
tion ; and I know of no instance where the improvements, 
effected by particular works, are more Mly and satis- 
fiictotily demonstrated, by a comparison of observations 
made previously and aubsequently to their execution. A 
notice of them will, I think, be interesting to engineers, 
not BO much as a record of what was done on the Tay, 
but as affording an illustration of the relation that exists 



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230 INLAND NAVIGATION. 

between the forms of a river's bed and its tidal pheno- 
mena, for it will be clearly seen in the caae of the Tay, 
that in altering its bed and the inclination of its sur&ce, 
many marked changes were effected on its tidal pheno- 
mena, while in those parts of the river where no works 
were executed the tidal phenomena were not altered. I 
propose, therefore, to ent^ into some detail as to the 
obstructions met with on the Tay, the means employed 
for their removal, and the effects produced on the tidal 
cxirrenta, as illustrating the subject of river improvements 



EivEE Tat. 

The river Tay, with its nmnerous tributaries, receives 
the drainage water of a district of Scotland amounting to 
2283 square miles, as measured on Arrowsmith's map. 
Its mean discharge has been ascertained to be 274,000 
cubic feet, or 7645 tons of water per minute. It is navi- 
gable as &r as Perth, which is 22 miles fix>m Dundee, 
and 32 from the German Ocean. The different points on 
the river hereafter to be referred to will be seen in the 
chart given in Plate XIV. 

Before the commencement of the works, certain ridges, 
called " fords," stretched across the bed of the river at 
diffOTent points between Perth and Newbm^h, and ob- 
structed the passage to such a degree that vessels draw- 
ing from 10 to 11 feet could not, during the highest tides, 
make their way up to Perth without great diflBculty. 
The depth of water on these fords, the most objectionable 
of which were six in number, varied from 1 foot 9 inches 



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APPLICATION OP THESE WORKS IN PBACTICB. 231 

to 2 feet 6 mcteB at low, and- 11 feet 9 inches to 14 feet 
at high water of spring- tides ; so that the regulating 
navigable depth, imder the most &.TourabIe circnim- 
stances, could not be reckoned at more than 1 1 feet. In 
addition to the shallowness of the water, many detached 
boulders lay scattered over the bottom. Numerous "fish- 
ing cairns," or collections of stones and gravel, had also 
been laid down, without regaxd to any object but the 
special one in which the salmon-fishers were interested, 
and in many caaes they formed very pTominent and 
dangerous obstructions to vessels. The chief disadvan- 
tage experienced by vessels in the unimproved state of 
the river was the risk of their being detiuned by ground- 
ing, or being otherwise obstructed at these defective 
places, so as to lose the tide at Perth, — a misfbrtime 
which, at times when the tides were falling from springs 
to neaps, often led to the necessity either of lightening 
the veaael, or of detaining her till the succeeding springs 
afforded sufficient depth for passing the fords. The great 
object aimed at, therefore, was to remove every cause 
of detention, and &ciLitate the propagation of the tidal 
wave in the upper part of the river, so that inward- 
bound vessels might take the first of the flood to enable 
them to reach Perth in one tide. Nor was it, indeed, 
less important to remove every obstacle that might 
prevent outwiurd-bound vessels from reaching Newburgh, 
and the more open and deep parts of the navigation, 
before low-water of the tide with which they 1^ 
Perth. ■ 

The works undert^en by the Harbour Commissioners 



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232 INLAND NAVIGATION. 

of Perth for the purpose of remedying the evfls alluded 
to, and which extended over edx working seasons, may be 
briefly described as follows : — 

1st, The fords, and many intermediate shallows, were 
deepened by steam dredging ; and the system of harrow- 
ing was employed in some of the sofl»r banks in the lower 
part of the river. The large detached boulders and " fish- 
ing e^ms," which obstructed the passage of vessels, were 
also removed. 

2d, Three subsidiary channels, or ofishoots fixim the 
main stream, at Sleepless, Darry, and Balhepbum islands, 
the positions of which will be seen on the plan, were shut 
up by embankments formed of the produce of the dredg- 
ing, so as to confine the whole of the water to the navi- 
gable channel, and the banks of the navigable channel 
were widened to receive the additional quantity of water 
which they bad to discharge. 

Sd, In some places the bants on either side of the 
river beyond low-water mark, where much contracted, 
were excavated, in order to equalize the currents, by 
allowing sufficient space for the &ee passage of the water ; 
and this was more especially done on the shores opposite 
Sleepless and Darry islands, where the shutting up of the 
secondary channels rendered it more necessary. 

The benefit to the navigation in consequence of the 
completion of these works has been of a twofold kind ; for 
not only has the depth of water been materially increased 
by actual deepening of the water-way, and the removal of 
numerous obstructions fix)m the bed of the river, but a 
clearer and a fi:eer passage has been made for the flow of 



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APPUCATION OP THESE WORKS IN PRACTICE. 233 

the tide, which now hegins to rise at Perth much sooner 
than before ; and as the time of high water is imaltered, 
the advantages of increased depth due to the presence of 
the tide is proportionally increased throughout the whole 
range of the navigation ; or, in other words, the deration 
0/ tidal influence has been prolonged. 

The depths at the shallowest places were pretty 
nearly equalized, being 5 feet at low and 15 feet at high 
water, of ordinary spring-tides, instead, as formerly, of 1 
foot 9 inches at low and 1 1 feet at high water. Steamers 
of small draught of water can now therefore ply at low 
water, and vessels drawing 14 feet can now come up to 
Perth in one tide with ease and safety. 

Such was the state of matters in 1845, when, during 
what has berai called the railway mania of that period, 
two companies proposed to cross the Tay by bridges be- 
tween Newbui^h and Perth. These schemes were natu- 
rally regarded by the navigation authorities as a great 
aggression on ihe rights of the public as proprietors of 
the highway of the river. In preparing a report in 
support of the views of the conservators of the river, 
it occurred to me that it was hardly sufficient to aver 
that so much gravel had been dredged, and so many 
fords had been removed, but that, if not essential, it 
would at least be Interesting to know what efiect the 
works had produced on the tidal action of the river. 
I accordingly made an elaborate analysis of the tidal 
observations, extending over ten years, which not only 
showed substantial improvements in the state of the 
river, but gave highly valuable information, which may 



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234 INLAND NAVIGATION. 

be held to be of general application. I am not aware 
that, previoufl to the publication of the Tay observBtionB, 
in the report to the Admiralty, on the railway bridge 
to which I have alluded, ihere had been any statement 
demonstrating the alterations on tidal flow produced 
by removing obstacles to its propagation; I accordingly 
submitted the result to the Royal Society of Edinburgh ;^ 
and as the sulgect is generally interesting in connexion 
with river engineering, I make no apology for giving the 
details in this treatise. 

The tidal observations to which I have referred were 
made at various times during a period of ten years, from 
1833 to 1844 inclusive, throughout the river and firth 
of Tay, at the following stations, viz., Dundee, which is 
marked Na 1 on the plan, Plate XIV. ; Balmerino, No. 
2 ; Flisk Point, No. 3 ; Balmbreich Castle, No. 4 ; New- 
burgh, No. 5 ; Carpow, No. 6 ; Kin&uns, Na 7 ; and 
Perth tide harbour. No. 8. The general results de- 
duced from these observations are given in the following 
tables, and show, by the favoiuable change which has 
been effected in the tidal phenomena of the eetuaiy, that 
the works executed fully answered the intended Kod- 

1. Propagation of Tidal Wave. 

The following table of elapsed times between arrival 
of the tide-wave, or commencement of the tidal flow, at 
the following stations, during sprivg tides in 1833 and 
1834, shows the rate of its propagation: — 



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Dg.zedb, Google 



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16 


DIltUMiD 

5 00 


RatoofTlda- 
WiTB In HUa 
pnHour. 

18-75 


29 


2-93 


606 


26 


204 


4-69 


53 


3-42 


3-86 



APPLICATION OF THESE WORKS IN PRACTICK 235 



Dundee to Balmerino, 

Balmerino to Flisk Point, 

FUsk Point to Balmbreicii, 

Balmbreicli to Ifewbargh, 

Newborgh to Perth (tide harbour), 2 30 8*66 342 

The result of obaervationa made in 1842, 1843, and 
1844, on spring-tides, give the same velocity, as above 
stated, between Dundee and Newbui^h, where no works 
bad been done, and the following rates between New- 
bui^h and Perth, below which place works had been 
executed : — 

Tim*. mitaiiH! <n '**'■ "' ^""e- 

nia«. Ulrtuioeui w.TslnltllM 

H. M. «Ji™. pet Hoot. 

NewbuTgh to Carpow, . . 25 1'33 3-17 

Carpow to Kinfanna, . . . 56 4-92 S-36 

Kinfauns to Perth (tide harbour), 20 2-32 6-93 

Giving as a mean for the whole 

dj^tuice from Newburgh to 

Perth in 1844, . . . 1 40 8-56 513 

Time from Newbuigh to Perth in 

1833, 2 30 8-66 342 

Thus showing an increase in the velocity of the tide-wave 
in the upper part of the river, which was improved, of • 
more than If mile per hour. 

The difference of the time in neap 'tides between New- 
burgh and Perth, in 1844, was 1 h. 53 m. 

2, ffigh-Water Level. 
The levels of the surface of high water at difFerent 
stations throughout the river have been found to be 
unchanged, and the following results refer to the years 
1833 and 1844:— 



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236 INLAND NAViaATION. 

From Flish Point to Balmbreicli tiiere is a fall of 6 m.A 
„ Balmbrelch to Newbnrgh there ia a rise of 7^ „ \ 
„ Newburgh to Perth (tide harbour) there ia spring-tidea. 

a rise of 18 „ / 

From Flisk to Balmbreich there is a fall of . 2^ „ \ 

„ Balmbreich to Newbui^ there is a rise of 6 „ I 

„ Newbnrgh to Perth (tide harbour) there ia ) neap-tides, 

arise of 12 „ I 

3. LovMoaier Level. 
Rist on Vie Sm/aee o/Lm-vxiter {Spring-Tides) in 1833. 



Ft. Id. 

Flisk to Balmbreich there vaa 




Biu of Blopa 


Ritiofndc 


a rise of . i 


204 


1-95 


4-69 


Balmbreich to Nevburgh, a 
rise of. . . . 2 8 


3-43 


9-35 


3-86 


Newburgh to Perth (tide bar- 
boor), a rise of . . 4 


8-56 


B-06 


3-42 



Sise on Sie LoumdoUt of Spring-Tides in 1844. 
Newburgh to Carpow, there is 

a rise of . . 6 1-33 3-75 3-17 

Carpow to Pertti, there is a 

rise of. . . . 17 7-23 263 

Hence fromNewbni^ toPerUi, 

1844, the rise is . . 3 866 280 6-13 

The result of the observ^tiona of 1844 thtis gives a 
depression on the level of the low- water mark of 2 feet at 
Perth tide harbour, the level of low water at Newburgh 
being unaltered. 

4. Duration of Flood and Ebb. 
The results of observations in 1833 and 1844 at New- 
burgh, where no works were executed, showed that the 



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APFUCATION OF THESE WOBKS IN PRACnCE. 237 

durations of flood and ebb tides at that place are un- 
changed. The tiinefl are as follows, being almost 'ideax- 
ticai in both years : — 

Spring-tides fltnr, 4 20 

„ ebb, r 20 

Neap^ides flow, 4 30 

„ „ ebb, 6 45 

At Perth, in 1833 :— 

SpriDg-tides flowed, 2 20 

„ „ ebbed, 7 

Neap-tddea flowed, 3 15 

„ „ ebbed, 7 

At Perth, in 1844 ;— 

Spring-tideB flowed, 3 10 

„ „ ebbed, 7 

Neap-tides flowed, 3 10 

„ „ ebbed, 7 

Increase in dniation of flood in springs at Perth, 60 

It will be observed from these tables that important 
changes have taken place in the part of ihe river that has 
been improved : — 

First, The fiJl on the sur&ce of the river from the 
tide basin at Periii to Newburgh in the year 1833 was 
4 feet, but after the works were executed it waB only 
2 feet. 

Second, In 1833 the passage of the tidal wave from 
Newburgh to Pertii (8*56 miles) occupied 2 hours 30 
minutes, being at the rate of 3'42 miles per hour ; but It 
is now propagated between the same places in 1 hour 40 
minutes, being at the rate of 5*13 miles per hour, — giving 



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238 INLAND NAVIGATION. 

a decrease in the time of 50 minutes, and an increase in 
the speed of the first wave of flood of more than 1^ mile 
per hour, since the commencement of the works. 

Third, The spring-tidea in 1833 at Perth flowed 2 
hours 20 minutea, and ebbed 7 houre ; but now the tide 
flows 3 hours 10 minutes, and ebbs 7 hours, — ^being an 
■increase in the duration of flood of 50 minutes. 

Fourth, It will further be noticed that on the part of 
the river between Dundee and Newburgh, where no works 
had been executed, the tidal phenomena remain imal- 
tered. 

River Foeth. 

The works on the Forth, executed under the direction 
of Messra. D, and T. Stevenson, produced changes on the 
tidal phenomena, which, in connexion with those de- 
scribed on the Tay, are interesting and instructive as re- 
gards the propagation of the tide, and therefore I shall 
briefly allude to them. The river between Stirling and 
Alloa is very circuitous, the distance by the navigation 
being lOj miles, while in the direct line it measures 
only 5 miles. The navigation was found to be impeded 
by seven fords or shallows which occur between Alloa 
and Stirling, and are composed of boulders, varying 
irom. a few pomids to several tons in weight, embedded 
in clay. 

It was determined, in the first instance, to remove two 
of these obstructions, viz., the "Town"andthe "Abbey" 
fords, which lie nearest to Stirling, and having the smallest 
depth of water, formed the greatest obstruction to the firee 



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APPLICATION OF THESE WORKS IN PEACTICE. 239 



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240 INLAND NAVIGATION. 

passage of vessels. The workB were commenced at the 
lower end of the Abbey ford, and were carried regularly 
upwards. The new channel excavated through this 
ford was about 500 yards in length, and 75 feet in 
breadth, and was deepened in some places about 3 feet 
6 inches. 

PrevioTifl to the commencement of the work, tide- 
gauges were erected in the positions marked 1, 2, 3, and 
4, in fig. 47, on which a series of observations was made 
for the purpose of establishing the original tidal pheno- 
mena of the river. Aiter the Abbey ford was cut through, 
further observations were made on the same gauges ; and 
it is to a comparison of these two sets of observations that 
I desire specially to refer. It is necessary to explain 
that gauge No. 1 is at Stirling quay. No. 2 about 500 
yards farther down, No. 3 at the top of the Abbey ford, 
and No. 4 immediately below it. It will therefore be 
understood that the Abbey ford, through which a channel 
was cut, lies between gauges Nos. 3 and 4. The whole 
of the gauges were placed on the same level, so that their 
readings might be more easily compared ; and the follow- 
ing are the results obtained with reference to the level of 
the low-water line : — 



Lerili ot Low anttr Lliit. 


» 


sn* 


£■? 


rr 


In 1847 the lov-water line vaa 
found to Btftnd at the following 
levels, 

In 1840, 

Depression, 


Ft m. 
2 
2 


n. ilL 

5 
3 6 


FL Id. 
5 S 
4 6 


PL fn. 
5 6 

5 





1 6 


9 


6 



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APPLICATION OP THESE WOBKB IN PRAOnCE. 241 

From this tabular statement we find that the low- 
water line at No. 4, which is below the site of the works, 
remains unaltered, but that it has fiiUen 1 foot 6 inches 
at the top of the Abbey Ford (through which the cut has 
been made). It fiirther appears that the formation of 
this cut has drained off the water, and lowered ihe sur- 
&ce 9 inches at gauge No, 2, and 6 inches at gauge No. 1, 
which is at Stirling. The former and present low-water 
lines and bed of the river are represented in fig. 47, in 
which is also shown by batched lines the amotmt of 
excavation on the Abbey Ford. This general depression 
of the river has of course altered the slopes or inclinations 
formed by the surfece of low water ; the slope between 
4 and 3 being decreased, while the inclinations between 
3 and 2, and between 2 and 1, have been increased in the 
following ratios : — 



..»-„ 


DlatUM. 


.«. 


,«,. 


DifftnaMio 

IHB. 


FMt 


InrliM 
puMU.. 


Indm 


Incliiutioii between 4 and 3, . 
Do. do. 3 and 2, . 
Do. do. 2«idl, . 


1550 
3050 
UOO 


122-6 
619 
11-31 


613 
20-77 
22-62 


-61-2 
+ 16-68 
+ 11-31 



Af^Eun, these changes on the low-water line have pro- 
duced corresponding alterations on the velocities of the 
first wave of flood, which are found to be as fol- 
lows : — 



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INLAND NAVIGATION. 



VclodtlM. 


1847. 


isu. 


niffeicjice. 


lllnats. 


MEiiateii. 


HluDtei. 


Time occupied hj first wave of tide 
in passing between gauges Nos. 

4 and 3, 

Do. do. Nos. 3 and 2, 
Do. do. Noi 2 and 1, 

Do. do. Nos. 4 and 1, 


SI 
6 
« 


8 

"J 
8} 


-16 

+ H 
+ H 


36 


28 


-8 



From this it appears that between Nos. 4 and 8 t^ere 
is an acceleration of 1 6 minutes, while between 3 and 1 
there is a retardation of 8 minutes, leaving the difference, 
or 8 minutes, as the actual amount of acceleration at 
Stirling, due to the removal of the ford and the lowering 
of the low-vra.ter level 6 inchee at that place. The rates 
of propagation in nulea per hour are as follows : — 



^.„^ 


1UT. 


.m 


»»» 


'sr 


'Sr 


4 and 3, 

Do. do. Nos. 3 and 2, 
Do. do. Noa. 2 and 1, 


-65 
5-77 
2-65 


2-2 
3-0 

1-87 


+ 1-65 
-2-77 
-0-78 



BelatioDS of the 
Blopei KDd raUs 
of tid«l pro- 
pagation. 



Theto observations and results throw some additional 
light on the circumstances which modify the propagation 
of the tidal wave. The table of the results obtained at 
the Tay shows that the (decreased inclination of the low- 
water lines of that river was attended by an acceleration 
of the velocity of the tidal wave ; and the above observa- 



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APPLICATION OF THESE WORKS IN PRACTICE. 243 

tions further show that a retardation has attended on in^ 
creased inclination of the low-water line of the upper part 
of the Forth. From the foregoing tabular Btatemraits it 
will be seen that between gaugra i and 3, where the 
slope has been decreased, the propagation has been accele- 
rated ; white between 3 and 2, where, &om the state of 
the works when the observations were made, it is found 
to have been iacreaaed, the rate of propagation had been 
sensibly retarded. It is worthy of remark, however, that 
the rates of propagation do not, either at the Tay or 
Forth, heair any constant relation to the dopes, but are 
modlBed by ^ther circumBtanceB ; in proof of which it will 
be found that the rate of propagation at the Forth be- 
tween gauges 4 and 3, where the slope is 61 '3 inches per 
mUe, is actually greater than between gauges 2 and 1, 
where it is only 22'62 inches per nule. The circum- 
stances of the Forth at this particular place axe somewhat 
peculiar. Before ihe Abbey Ford was cut through, it 
acted as a dam extending across the river, and had the 
effect of increasit^ the depth at low water all the way up 
to Stirling. By cutting the channel through the ford, 
however, not only has tfie water been drained off and 
rendered shallow, but its surface has beeif broken by the 
projection of boulders from the bottom, which formerly 
were entirely covered; and while this ©Sect has taken 
place in the upper part of the river, a comparatively 
smootii cut, with r^ular sides and bottom, has been 
formed in the Abbey Ford, through which the river flows 
at low water in a body of considerable depth. I there- 
fore atteihute the slow propagation of the tide betweffli 



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244 INLAND NAVTOATIOS. 

2 and 1 to the shallowness of the water and the very- 
rugged state of the bottom, which is in many places 
completely studded with boulders, risiug some above the 
suT&ce at low water, and others to within a few inches 
of it ; while the high velocity up the steep slope of the 
ford is to be attributed — Ist, To the depth of water 
caused by the whole river being made to pass through a 
comparatively narrow channel ; 2d, To the rectangular 
cross section of the cut ; and 3d, To the smoothness of 
the sides and bottom. At the Firth of Dornoch again, as 
already noticed, between the Quany and Bonar Bridge, a 
distance of 1 mile, although the water is shallow and the 
bottom rough, it is not, on ihe whole, more so than be- 
tween gauges 1 and 2 on the Forth ; but at the Dornoch 
the slope on that mile is no less than 6 feet 6 inches, and 
the rate of propagation is only two-thirds of a mile per 
hour. Moreover, it was fomul that the tide did not b^n 
to show at Bonar imtjl it had risen 6 feet 6 inches on the 
gauge at the Quarry, being the exact difference of level 
between the two points of observation. 

These various results as to slopes and rates of pro- 
pagation, as well as others which have come imder my 
notice, seem to justify the following deductions as to the 
propagation of the tide-wave in rivers with sloping sur- 
feces and irregular bottoms, which, as stated at page 158, 
may be regarded as an addition to the laws formerly 
stated as regulating tidal propagation. These results are 
as follows : — 

1st, That a decrease of slope is followed by an accelera- 
tion of the rate of propagation of the tidal wave. 



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r 



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AITUCATION OF THESE W0BK8 IN PaACmCE. 245 

2d, That an iuct^ase of slope is followed by a retarda- 
tion of the rate of propagation. 

Bd, That the rate of propagation does not beta: any 
constant relation to the amount of slope, although it is to 
soine extent modified by it. 

ith, That while the rate of propagation in rivers is in 
some measure due to the depth of water, it is neverthe- ■ 
less influenced by ike slope of the sur&ce, the form of the 
channel, and the obstructions protruding from the sides 
or bottom. 

5th, That, if not in all cases, at least when there are 
steep slopes and shallow water, as at the Dornoch Firth, 
the level of the crest of the wave must i-ise to the level 
of the surface of the water (or perhaps the bed of the 
river) above it, before a progressive motion takes place ; 
and 

Gth, That, firom the difBculty of dealing with so many 
variable elements, it is impossible, in many rivers, to 
determine the ruling circumstances which can be held as 
regulating the rate of tidal propagation. 

RiVEB BiBBLE. 

The Bibble in Lancashire, as shown in Plate XY., 
the improvements of which were designed by Messrs. 
Stevenson, presents an example of a gt^at amount of 
additional depth having been obtEoned in a compara- 
tively short space of time. That river, according to 
Mr. Park, who conducted, as resident engineer, the 
greater part of the works, has a coiurse of 82 miles, and 
drains 900 square miles of the counties of York and 



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246 INLAND NAVIGATION. 

Lancaster. The formation of ite bed rendered the state 
of the tidal compartment previous to the improvements 
very defective. The bottom in the lower part of the river 
conmsts of loose sand, while that of the upper reach is 
alternately compact gravel and sandstone rock. About 
half a mile below Preston, in particular, it was found that 
a solid ridge of sandstone, extending to 300 jaxda in 
length, stretched quite across the channel Its sur&ce 
was from 3 to 5 feet higher than the general bed of the 
river both above and below it, and so prominent an 
obstruction did it form that the higher parts of the rock 
were occasionally left dry during the long droughts of 
summer. The propagation of the tidal wave and free 
flow of the currents were checked on approaching it, 
whUe the power of the tidal and fr^-water scours was in 
a great measure neutralized, and rendered almost unavail- 
able in keeping open the upper and lower stretches of the 
navigation ; so that its influence in obstructing the river 
resembled that of a great artiflcial weir stretching across 
the stream. In proof of this it may be stated that the 
ordinary rise of spring-tides at Lytham, which is 12 miles 
seaward of Preston, is about 19 feet,' and that of neap- 
tides is 14 feet, while at Preston, prior to the operations, 
the rise of spring-tides did not exceed 6 feet, and neap- 
tides of 13 or 14 feet rise at Lytham did not reach 
Preston at alL The removal of the rock which encum- 
bered the bed was naturally viewed as the most urgent 

' Cftpti^D Sir Edward Belcher, while eogiged in making the Admiralty Sarrey 
of th« Ribbl^ found that on one ocoasion the tide at Lytham roae SS feet 
7} inches. 



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APPUCATION OF THESE WORKS IN PRACTICE. 247 

and important work for effecting an improvement in the 
tidal phenomena and general depth of water. To this, 
therefore, the Navigation Company £rat directed ita at- 
tention, and, as has been noticed in Chapter VlIL, suc- 
ceeded in removing the rock, and further, in dred^ng 
many thousand tons of gravel, and erecting about 18 
miles of rubble tnuning walls. I have already given 
some details as to these works, and I have only to add 
here that they have effected a striking improvement on 
the navigation. Mr. Garlick informs me that, at "the 
Chain," below Preston, the level of the low vraiter is now 
6 feet 8 inches lower than it was in 1841, before which 
period the works had begun to show their effect. So 
that it is safe to condude that the total lowering of the 
low-water line is between 7 and 8 feet, and the tidal 
range has been inct^ased to the same extent, and the 
tidal propagation, when I had occasion to ascertain it 
some years ago, was found to have been accelerated 
upwards of an hour. The practical result of this im- 
provement is that vessels to which the navigation was 
previously at all times cloaed, can now come up to the 
quays at Preston with comparative ease and safety, even 
in neap-tides. 

RrvEB LUNB. 

The works on the Lune in LancaEdiire were executed by 
Messrs. Stevenson, under the direction of the Admiralty. 
They consisted in removing fords by dredging, shutting 
up subsidiary channels, and erecting liver walls. Like all 
rivers flowing through tracts of sand-banks, the Lune was 



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248 INLAND NAVIOATION. 

ever cbangmg its course, and in order to iUustiate tliis I 
have shown on Plate VIII. the channel of the Lune in 
August 1847, August 1848, and December 1848, taken 
fi^am actual survey. The great object of the improve- 
ments waa by removing obstructions and making training 
walls BO to regulate -the currents as to insure a fixed 
channel and a greater deptL Fig. 48 shows the gradual 




change efiected on the low-water line in consequence of 
the works. The upper line shows the surfece of the 
river in 1838, the intermediate line in 1848, and the 
lower line in 1851. The general effect has been to 
increase the depth of water up to the quays at Lancaster 
about 4 feet, and to prolong the duration of the tidal 
influence at that place 30 minutes in neap and one hour 
and a half in spring tides ; so that vessels can approach 
and leave Lancaster much earlier than formerly, while the 
improved channel is navigated with much greater ease. 

RrvEE Clyde. 
The Clyde affi)rda a striking proof of the extent to 
which river improvements may be carried. So insignifi- 
cant was the stream in its natural state, that Smeaton, in 



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APPUCATION OF THESE WORKS IN PRACnCE. 249 

1755, proposed to erect a dam with locks in the lower 
part of the river, and to convert it into a tidal camd in 
order to bring craft drawing 4 feet 6 inches up to Glas- 
gow. In 1768, however, Golbume surveyed the rivOT. 
He found that as &t down as Eilpatrick the depth of 
water was only 2 feet, and recommended the con- 
struction of a aeries of jetties &om either side, for the 
purpose of narrowing and deepening the stream. This 
may be held to have been the commencement of the 
improvement of Hie river Clyde, which now admits 
vessels drawing 22 feet to steam up to Glasgow. The 
reader must not however suppose that this result has 
been attained by means of the jetties which were erected 
under the advice of Golbume. It was soon discovered 
that this object could not be gained by such works, and 
it was not until the ends of the jetties were connected 
by longitudinal walls, and until dredging machines were 
extensively employed, that the Clyde improvements began 
to assume an importance conunensurate with the vast 
commercial interests of the city of Glasgow and 8ur~ 
rounding districts. Even so recently as 1836, Mr. James 
Walker was asked to report to the Trustees on a 
scheme to construct a canal from Bowling to Glasgow. 
It is, indeed, since 1836 that the Clyde Navigation may 
be said to have made its most important progress towards 
its present state, and this has been achieved in a great 
measure by widening the river where it had been impru- 
dently contracted, and by dredging on an enormous scale, 
as I have already stated in Chapter YIIL, under the 
head of Dredging, and nothing now can avail to remove 



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250 INLAND NAVIGATION. 

continually growing obstructions, and to keep the naviga> 
tion open, but an unremitting application of steam power 
applied to the beat advantage. It would have been very 
interesting, in such a case as the Clyde, which, I may say, 
from being a fresh-water stream has been converted into a 
great tidal channel, to have possessed accurate records of 
the ori^al and present levels of the low-water lines of 
the river. 

It is not possible to arrive at a correct estimate of the 
actual extent to which the low-water level of a river has 
been lowered, unless an accurate record has been kept of 
the levels with reference to a fixed bench-mark. The 
lowering of the low water is a slow process, and the eye 
gradually becomes associated from year to year with an 
entirely altered state of the river, which, if it had 
occurred in the course of a night, or even a week, 
would have struck even a casual observer with amaze- 
ment. It is, I believe, impcwaible now to arrive at the 
extent to which the bed of the Clyde has been lowered 
since the days of Golbume, as the old plans do not specify 
a proper datum for reference. But having occasion to ia- 
quire into this with reference to a judicial question on 
which I was instructed to report to the Court of Session, 
I found the means of arriving pretty accurately at the 
extent the low-crater line had been lowered since 1853 
at Erskine Ferry and West Ferry, the former 9 J, the latter 
1 34 miles from Glasgow ; and the following table gives tiie 
results as reported by me to the Court. But even these 
figures may be subject to some correction, due to the state 
of the river when the observations were made : — 



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APPLICATION OP THESE WORKS IN PRACTICE. 251 
Tabdiar Vibw of thb Ekiativk Lbtels 07 Low Watzk at 

VARIOUS DATES FROM 1853 TO 1868. 
Ltnlibalov Wtsi Femf. 

IS'OO. IjOt water on cross sections, 1863 ; hy Thomas Kyle. 
18*08. Low water, spriDg, 1653, on section ; l^ Thomas Kyle. 
18'17. Low water, average epring, April to September 1S63 ; note 

on plan by Thomas Kyle. 
18'56. Low water, spring, 20tk March 1840; sections by Thomas 

Kyle. 
19'33. Low water, spring, 17th September 1868; reported by 

David Stevenson. 

En^ne Ferry. 
17-00. Low water, spring, 1653, on longitudinal section ; by 

Thomas Kyle. 
17'15. Low water, spring, 1863, on cross sections; by Thomas Kyle. 
17'42. Low vater, average spring, April to September 1853 ; note 

on plan, by Thomas Kyle. 
17'61. Low water, spring 20th March 1640, on section; by 

Thomas Kyle. 
17'60. Low water, on contract plan, by John F. TJre, dated 10th 

April 1666. 
18-18. Low water in 1866 and 1867. 
18-70. Low water, spring, 19th September 1868; reported by 

David Stevenson. 

NoU. — The datam to which the levels refer Is the surface of the 
cope of South Quay wall of Glasgow harbour, as defined in plan 1 86 3-4, 
by Thomas Kyle. 

In lie upper part of the river Mhe lowering of the bed 
has been much greater. In 1832, the late Mr. Robert 
Stevenson erected Hutcheson Bridge, which croeaed the 
Clyde at the site of the new Albert Bridge. The masoniy 
of the piers of Hutcheson Bridge was laid at the level of 
7 feet below the bed of the Clyde, on a platform of timber 
on piles 18 feet in length. I &und by a section made in 



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252 INLAND NAVIQATION, 

1845, after a lapse of thirteen years, that the level of the 
river had been lowered, in consequence of the improve- 
ments of the Clyde Trustees, no less than 11 feet, and 
even with that amount of scour the bridge was, and 
might long have remained, a safe structure. But imme- 
diately above its site there is a weir which dams up the 
Clyde and forms a lake, or almost still pool, for several 
nules. It was determined to remove this weir, and after 
its removal the bridge could no longer be pronounced 
safe; and it has been accordingly replaced by the pre- 
sent structure. 

It is right to state, with reference to the removal of 
the Clyde weir, and as to what I have said on the sub- ~ 
ject in Chapter VI., that the removal of weirs, viewed 
as an abstract question, is in general a safe and even 
proper navigation improvement. But in the case of the 
Clyde weir, to which I have alluded, two questions were 
urged by the opponents of the measure. The first was, 
whether the damage to the banks, and the amount of 
stuff which would be sent down into the lower harbour, 
would not occasion more expense to dredge it than could 
be compensated for by any increase of scour due to the 
removal of the weir ? And the second, and perhaps more 
important, question was, whether, as a sanitaiy and 
am^ty question, it was desirable to sacrifice the lake 
formed by the weir, and used for bathing and boating 
by the great population of Glasgow f I thought it was 
better that the weir should remain; but this is a question 
more for the community of Glasgow than for engineers to 
determine. 



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APPLICATION OF THESE WOBES IN KUCTICK. 253 

RiTEB Tees. 
I shall only Airier refer to the Tees, as affording 
an example of a navigation where improvement was 
long deferred in consequence of advice which was not 
calculated to attfun that object. I am indebted to 
Mr. John Fowler, of Stockton, the Eng^eer to the Tees 
CommissionerB, for the information concerning ihai river. 
"Without going back to its very early history, it is suffi- 
cient to say that in 1804 Mr. Chapman found that the 
available depth up to Stockton was 9 feet at spring tides, 
and at Cargofleet, five miles below Stockton, there was a 
shoal with only 2 feet at low water. Following out his 
report, the Tees Navigation Company was incorporated 
— the Portrack cut was executed, and opened in 1810, 
and effected, some improvement. It does not appear 
that much more was done till 1827, when the Navi- 
gation Company consulted Mr. Bobert Stevenson of 
Edinburgh and Mr. H. Price. Both of these eng^eers 
reconmiended another cut to be formed, as already noticed 
at page 196, but they differed in opinion as to the general 
treatment of the river. Mr. Price recommended that 
it should be contracted b^ jetties, and Mr. Stevenson 
that the banks should be &ced with continuous walls, 
stating as his reason for this recommendation, " that to 
project numerous jetties into the river I regard as inex- 
pedirait, being a dangerous encumbrance to navigation, 
and tending to disturb the currents and destroy tibe uni- 
formity of the bottom," The plan adopted by the Navi- 
gation Company was however that of Mr. Price, and jetties 



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254 INLAND NAVIGATION. 

were constructed on the river to a large extent, and Mr. 
Fowler aaya " that after a trial of twenty-seven years it 
was found tiiat they were liable to all the objections that 
had been urged against them by Mr. StevensoiL" Accord- 
ingly, under Mr. Fowler's direction, the whole of the 
jetties have been removed, and the river is now guided 
between continuous walls in the upper part of its course, 
and low training walls, similar to those in the Kibble and 
other rivers, have been constructed in the lower reaches. 
The result of the operations carried out 1^ Mr. Fowler is 
that there is now an easily maintained chmmel having a 
navigable depth of 18 feet up to Stockton, where, besides 
the ordinary traffic of the district, there is a lai^ ship- 
building trade, launching steamers of 3000 tons burden. 

Many instances might be referred to where a course 
of treatment opposed to that which I have recommended 
has not been followed by favourable results ; but I deem 
it sufiScient to confine my remarks chiefly to an expoation 
of the correct principles of river improvement, without 
discussing at length erroneous practice or its baneful 
results ; the more so as these have been most fully and 
ably treated by Captain E. K. Calver, E.N., whose 
investigations into the former and present state of some 
of our' tidal rivers are of great value to the hydraulic 
engineer.^ 

> The Ctmaenx^oa and ImproBemeni of Tidal Sivert, by E. K. C&Iver, R.N. 
London, Weale, 1853. 



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CHAPTER X. 

SITUATIONS WHERE THE PRINCIFLBS OF lUPROTEHENT 
BECOMUENDE^D ABE NOT AFFIJCABLB. 

It ia necMsary, however, to state that in certain mtua- 
tions the principles of river improvement which I have 
advanced will he found to be of veiy limited application. 
Such cases, indeed, are rarely to be met with, but still it is 
necessary to notice them. I allude to rivers where the 
tidal or intermediate compartments are, from natural 
causes, of veiy Bmall extent. 

The Ebke. 
To illustrate what is meant, I refer to the Erne in 
Donegal, which has a tidal capacity of only 2^ miles, 
extending from the bar up to the town of Ballyshannon, 
where the tidal flow is terminated by what is called the 
" Salmon Iieap," a perpendicular bed of rock extending 
across the river, and rising to a height of 1 5 feet, over 
which the river forms a cascade. This water&U forms 
the limit of the tidal flow, beyond which it could not, 
without works of a gigantic character, be extended. 

The Ness. 
Another case is the Nees, where, indeed, althoitgh 
there is no waterfell, there exists perhaps a no less seri- 



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256 INLAND NAVIGATION. 

ouB obstacle to tidal flow. The river at present passes by 
a bending channel from Inverness to the Beaulj Firth at 
Eessock Boads, a distance of about 2 miles. A scheme 
was proposed in 1847 for making a straight cut to obviate 
the great difficulty which vessels have in making their 
way from the Beauly Firth to Inverness, a diflBculty which 
was mainly attributed to prevailing adverse winds, due 
to the configiuation of the surroimding hilla But on 
making an investigation, with a view to reporting on the 
proposed improvement scheme to the Admiralty, it was 
found that the difScultaes attending the navigation of the 
river are mainly the prevailing outward currents due to the 
physical conformation of the bed of the Ness, which may 
be shortly described, as it iUustrates' generally a class of 
rivers which are very difficult to improve : — 1st, The rise 
of ordinary spring-tides at the moutt of the river is 14 
feet; 2d, The distance to which the influence of such 
tides extends is only about 2 milee, which comprises the 
whole tidal compartment of the river ; 3d, the slope or 
inclination of the low-water line of this tidal compartment 
is 'no less than 7 feet per nule, and the tide takes from 
2 to 3 hours to make its way up the first mile ; Atk, 
The natural result of such a state of matters is, that no 
tidal current is generated at the mouth and propagated 
up the stream, and consequently the phenomenon of a 
current, due to flood-tide, may be said to be almost un- 
known. 

Under these circumstances the main barrier to free 
navigation of the river Ness may be traced to the absence 
of a tidal current, to aid the entrance of vessels from 



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THE NESa. 



Kesflock Roads, and assist their progrras up the quays. 
This part of a ship's voyage is at present eflfecfced by help 
of men and horses, which drag the vessel against the 
nearly constant downward current, which varies in 
strength with the amount of water discharged hy the 
river Ness, during its frequent heavy floods. 

The eadstence of a moderate amount of &11 or slope on 
the low-water line of a river, is a hopefiil feature in its 
capalnlities for improvement ; while, on the other hand, 
such a slope as that on the Ness proves a great barrier 
to its extended improvement as a tidal river; for it is 
obvious that to obtain on that river a slope sufficiently 
gCTitle for easy navigation, it would be neceasary to lower 
its bed to BO great an extent, and to execute works of 
such magnitude, as to render it inexpedient to entertain 
such a project. 

The two instances I have given will suffice to illustrate 
those cases, happily not very numerous, which do not 
come within the range of what I may term improveable 
rivers, for in either of the cases I have named, works of a 
magnitude wholly disproportionate to the benefit to be 
derived would be requisite, in order to remove the 
. obstacle which nature has opposed to the existence of a 
navigable tidal channeL 



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CHAPTER XI. 

WOBKS FOR ACCOMMODATION OF VBSBEM, 

Doeka — Tide-faamn* — Oroynea — Biver quays ; ezamplra □( tlioae kt Belbat, 
Londoudeny, and Uie Clyd«. 

The works I have already described are for fecili- 
tating the ingress and egress of Tessds. In addition to 
this, it is necessaiy to provide for their accommodation. 
For this purpose it is desirable, where ihe currents are 
strong, to afford them some protection against heavy 
floods accompanied by ice, which are often very destruc- 
tive to shipping. 

On a large scale this protection is afforded by docks 
entered by tide locks, and constructed in all respects like 
the wet docks in any of our seaports, and they may 
therefore be held to be a claes of works common to all 
harbours, and not specially connected with tidal rivers. 
There are some works, however, that are essentially river 
works, and these it is necessaiy shortly to notice. 

Among them are what are termed tide-basins, which 
are artificial cuts retiring from the stream, having their 
sides bounded by quays or wharves, into which vessels 
may be withdrawn and sheltered from the current, but 
where they are still liable to take the ground at low water. 
The Kingston dock at Glasgow is a large tidal basin of 



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WORKS FOR ACCOMMODATION OF TBSSEIfl. 259 

this kind, being in &ct a dock without locks or gates. 
But it is sometimes desirable on a smaller scale to protect 
the berthage of quays along rivers from currents or ac- 
cumulations of gravel This was done at Inverness by a 
weir or groyne of timber work, which is shown in eleva- 
tion and cross section, %. 49. It extends in front of 



the quays, and prevents the current of the river in floods 
from shoaling the berthage by heaping up gravel I have 
seen a protection on a very large scale at Albany, on tte 
Hudson, where the vessels navigating that river, and 
trading with the Erie Canal, are accommodated in a large 
basin of thirty-two acres. This basin is separated from 
the current of the Hudson, and the ice it sometimes brings 
down, by a longitudinal mole or pier of about three- 
quarters of a mile in length, left partially open for scour 
at the upper end, and connected to the shore by draw- 
bridges. 

In many fdtuations where currents are not vety strong, Rinr quri. 
and the river is sufficiently wide to admit of vessels being 
moored in it, aa at the Clyde, or the Foyle at London- 
deny, the berthage for vessels is very conveniently 



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260 INLAND NAVIGATION. 

afforded by forming lines of quays along the shore. Such 
quays, indeed, constitute an important part of all har- 
bours which are formed in tidal rivers ; and in illiistration 
of some of the various methods of construction adopted in 
Bwch cases, I may give the following cross sections. Fig. 
50 shows the timber whai^ige constructed by Mr. Smith 



at Beliast, which is composed of a &cing of timber-work 
secured by iron ties fixed to piles, the space behind the 
framework being filled up and the roadway formed at the 
top. Fig. 51 is a plan showing the positions of the piles 






and ties. Sometimes a similar fiice-work is employed, 
backed by a wall of concrete, and iron plates have also 
been used for the fiwing instead of planking. Figs. 52 
and 53 are a section and elevation of the quays at Lon- 
dondeny, designed and executed by Messrs. D. and T, 



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WORKS FOB ACCOMMODATION OF VESSEI^. 261 

Stevenaon. At this place the ground is very soft, and in 
order, as much as possible, to reduce the weight, the front 



Fio. 62. Pio. 63. 

compartment of tte wharf next the river is left open. 



Figg. 54 and 55, again, are sections of the stone wharves, 
constructed from a demgn by Mr. Walker, at Glasgow, 



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INLAND NAVIGATION. 



under the superintendence of Mr. Ure. Fig. 54 is the 
section adapted to a clay hottom; and fig. 55 is that 
which is adopted when the hottom consists of sand. In 



both cases the depth of water in front of the quays is 
20 feet at low water, aad is intended to accommodate 
merchant vessels of the laigest class. 

These examples of whar&ge on tidal rivers will serve 
to show the student the structures designed by different 
engineers as applicable to situations where the foundation 
is hard or soft. 



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CHAPTER XII. 

"sea-eeopee" oompabtment op bivees. 

Ban i theoriea to account for the fonnfttLon of — Origiii of baia, as illnatrated hy 
the DoTDoch Rrth ; Cutelli'B theory of the fonnatioii of ban ; Muditioii* 
nnder which ban are formed — Barlen riren — Bar at Cochin — Depth over 
ban dae to bcoqf — ComparisoD of rirer and tidal water in ettnaries — Back- 
water ; its importance for acoiuiiig ; difiemnt aapecta under which baokwator 
may be viewed, ai iHnatrsted b; Hartlepool alahe, Montrose basin, and WtJ- 
laaey Fool — Lerel at which backwater ia abatracted — General ptopoeitiona 
r^arding backwater — Lower parta of ettnaries, luch aa the Meney, etc, 
cannot be improved nnleai at great coat — Ban of snch riven m the Tyne and 
Wear may be improved by protecting pien — Bar of the MiHsianppi — Bar of 
the Danube ; its canai^ and worki for ita improvement — Hard bars — Qroynea. 

Many of the works described in Chapter VTIL, such 
as tnuning walls and dredging, ate not more applicable 
to the " tidal " than to the " sea-proper" compartment, 
the distinguishing features of which, are the phenomena 
attending the flow of rivers or bodies of tidal water into 
the sea. 



In some instances, snch, for example, aa the Forth, 
the junction of the eetuaty with the sea occuis without 
occasioning any very perceptible or marked disturbance 
of the currents or change on the bed of the channel, so 
that a ^p may, at any tdme of tide, run without check 
or hindrance from the Isle of May to St. Margaret's Hope. 
But in Una req>ect t^e Forth is exceptional The en- 



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264 INLAND NAVIGATION. 

trances to almoat all British, as well aa ContiQental, rivera 
are interrupted by what is termed a " bar." Its origin is, 
indeed, not always to be traced to the same cause, but 
the Mersey and the Tay, as well as the gigantic Nile and 
Mississippi, hare the same troublesome feature, which is 
not only very hurtfiil to navigation, but is pOThaps the 
most difficult subject with which the marine eqgineer has 
to grapple. 

A " bar," in nautical language, is the name applied to 
the shallowest part of the navigable channel through the 
sand-banks which generally collect at the mouths of 
eatuoriea It may perhaps best be explained hy an 




illustration. Fig. 56 is a diagram, on which the dotted 
line shows the &irway or deepest channel through the 
sand-bankfl. It will be seen that the place marked " the 
bar " lies at a considerable distance from the shore, and 
has extensive sand-banks, drying at low, but covered at 
high, water, as well as submerged sandbanks which never 
dry, on either side of it. Fig. 57 is a longitudinal section 



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"sea-propeb" compabtment of eivees. 265 

made on the dotted line, and represents the depth of 
water on an enlarged scale From this it inll be under- 




stood that the bar is the shallowest part of the channel, 
there being deep water both landward and seaward of 
it. What is termed " the bar," therefore, is not the sand- 
bank that dries at low water, but those constantly sub- 
merged banks which have a channel, subject to variations 
in position and depth, passing through ihem. 

The bar then r^ulates the navigable depth, and no 
passage over it can be obtained until the tide has risen 
sufficiently high to enable vessels to cross it ; and it is 
more or less marked and decided according to certain 
conditions to be afterwards explained. "We accordingly 
find great variety in the depth of water. For example, 
The bar of t^e Mersey has a depUi of &om 9 to 1 feet at lo7 water. 

Tyne „ 6 to 7 

Wear „ » to 4 

Eibble „ 7 to 8 

Tay „ 16 to 18 

Dee „ 10 to 12 

And while these limited depths exist on the bar, 
there is in most cases ample depth within or landward 
for vessels of the largest class to lie afloat at all times 
of tide. At the Dee, for example, the celebrated anchor- 
age of " Mostyn Deep," affords depth and area for almost 
any fleet of ships. 



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266 INLAND NAVIGATION. 

Many theories have been propounded to account for 
the phenomenon of the " bar." What may perhaps be 
termed the most fiivourite theory is, that bars are com- 
posed of materials held in suspension by the river, and 
depomted so soon as its current is checked by meeting 
the still water of the ocean. This idea will be found 
stated by various authorities, as expr^sed in the follow- 
ing quotations : — 

" When the flood matters meet the incoming tide, 
there must necessarily be a deposit." 

" The position of a bar is at the point where the 
opposing forces meet or balance. The material held in 
suspension by water, travelling at a certain velocity, &Us 
to the bottom and forms a deposit where that velocity is 
checked," 

"The incoming tide, when it meets the water dis- 
charged by the river, checbS the velocity of this water, 
and so causes a deposit, which forms the bar." 

Many other similar quotations could be g^ven. But 
this theory, at all events as regards " sea bars," of which 
we are now treating, is disproved by such a case as 
tbe Dornoch Firth. The bar at that place occurs at a 
point 14 miles seaward of the point at which the river 
enters the sea, as wiU be seen in Plate IV. The idea that 
sand-banks of such magnitude as those at the Dornoch 
Firth could be formed by the detritus brought down by 
the small rivers OykeU and Cassley, which flow into the 
upper end of the firth, is wholly imtenable, and is indeed 
contradicted by the &ct that the bar and adjoining banks 
are composed of pure sand, and not of alluvial matter 



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"SEA-PROPER COMPARTMENT OF BIVEBS. 267 

deposited by the river, as will afterwards be more fully 
alluded to. 

Anotlier tbeory attributes bars to the want of suffi- 
cient scouring power ; but this as an abstract statement 
is unwarranted when we £nd bars existing at the mouths 
of such rivers as the Miasisaippi. 

Another theory attributes the o&seTioe of a bar to 
" the presence of a nearly equal dura.tion of the p^od 
of ebb and flow in the lower reach of the river, aocom- 
paiiied by an extremely gentle inclination <^ its sur&ce 
at low water." ' To refer again to the Dornoch FirUi : we 
have an equal duration of the ebb and flow throughout 
the firth, and the level of low water practically the same ; 
and yet there exists as p^ect a specimen of a bar at the 
mout^ of the flrth as can possibly be imagined. We can- 
not, therefore, in endeavouring to account for the exist- 
ence of bars, or the exemption from Hiern, accept any of 
these explanations. 

Since 1842, when I had occasion to bestow much origin or a 
attrition to the subject, I have never had any difficulty 
la tracing the accumulaticms which give rise to all such 
bars as those of the Mersey, the Eibble, the Tyne, the 
Dornoch, or the Tay, subject to the conditions hereafter 
stated, solely to the action of the sea. The waves, as is 
well known, throw up a girdle of light or heavy material, 
varying witii the exposure from sand to boxilders, roimd 
every bay and headland of oiur coast ; and the entrances 
to rivers form no exception. The effect of this constant 
action of the sea is to form a continuous line of beach 

1 Trtatite m l\e InproveBifaU qf At Jfatngation of &W*, bjr W. A. Brooks, 



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268 INLAND NAVIGATION. 

across the mouths of all our tidal rivers and inlets ; and 
such a beach would very soon be made, did not the flow 
of the tidal currents maintain an open channel through 
it. In this way the waves of the sea on the one hand, 
and the currents on the other, produce the well-known 
feature of a tide-covered beach extending firom the shores 
of our inlets, with submerged sand-banks, having a channel 
through them termed the " bar." 

This explanation is given in a report made in 1842, in 
which it was necessary to investigate the cause of the 
" bar " at the Dornoch Firth, from which the following is 
an extract : — 
Bit kt Dornoch " This bar is an accumulation of hardish sand-banks, 
through which there is a navigable feirway of not less 
tban 9 feet at low, and 22i^ feet at high water, of ordin- 
ary spring-tides. It appears to be rettuned in its present 
state by a combination of agents. The heavy sweUs from 
the German Ocean, with which the coast is visited, have 
a tendency to heap up the sand from the adjoining shores ; 
but this tendency is, to a certain extent, counteracted by 
the tidal and firesh-water currents of the firth, and the 
result of their joint action is the bar — a bank, or series 
of banks, of considerable extent, permanently imder 
water, through which there is a deeper passage or feir- 
way, whose depth of water is believed to remain pretty 
much the same, although its direction occasionally 



But I cannot altogether claim to be the author of this 
explanation of the origin of bars, as I afterwards dis- 
covered that a suggestion in some respects the same had 



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"bka-pboper cohpabthent of biters. 269 
been given about two centuries ago by the Abbot Caatelli, cuteiii'aUiMMT 

,. of tlie f ormitloD 

who wrote as follows:' — "As to the other pomt of tneofb«™. 
great stoppage of porta, I hold that all proceedeth 
from the violence of the sea, which being sometimes 
disturbed by winds, especially at the time of the waters 
flowing, doth contiaually raise from its bottom immense 
heaps of sand, carrying them by the tide and force of 
the waves into the lake; it not having on its part 
any strength of curreat that may rise and cany t^em 
away, they sink to the bottom, and so choke up the ports. 
And tJiat this effect happeneth in this manner, we have 
most frequent experience there<rf along the setujoasts ; 
and I have observed in Tuscany, on the Eoman shores, 
and in the kingdom of Naples, that when a river &lleth 
into the sea there is always seen in the sea itself, at the 
place of the river's outlet, the resemblance, as it were, of 
a half-moon, or a great shelf of settled sand under water, 
much higher than the rest of the shore, and it is called in 
Tuscany il cavcdlo, and here in Venice, lo seanto ; the 
which Cometh to be cut by the current of the river, one 
while on the right side, another while on the left, and 
sometimes in the midst, according as the wind fita And 
a like effect I have observed in certain little rillets of 
water along the Lake of Bolsena, with no other difference 
save that of small and great" 

Had the Abbot ended his statement here, it would have 
been identical with that I have suggested, but he goes 

' The Menttiralim o/Bumunff Waters. By Don BeDodetto Castelli, Abbot of 
St. BoiMdetto Aloftio, and ProfsBBor of the Mtiihemfttici to Pope Urban VIIL in 
B«me ; faansUted by TbomM Salnabniy, E>q , London, 1661. 



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270 INLAin) NAVIGATION. 

on to Bay, "Now whoeo well considereth this effect plainly 
seeth that it proceeds fi'om no other than from the con- 
traiiei^ of the etream of the river to the impetus of the 
sea-wavea ; seeing that great abundance of Band, whidi 
the sea continually throws upon the shore, cometh to he 
driven into the sea hy ike stream of the river, and in 
ih&t place where these two impedimenta meet toith equal 
Jbrce, the sand settleth under water, and thereupon is 
made that same shelf or cavalh ; the which, if the river 
carry water, and that any considerable store of it shall be 
thereby cut and broken, one while in one place, and the 
other while in another, as hath been said, according as the 
wind blowB ; and through that channel it is that vessels 
&M down into the sea, and again make to the river, as 
into a port." 

The words which I have italicised apeak of sand 
" driven into the sea by the stream of the river," and of 
the place where the sea and the river meet with " equal 
force," causing the sand " to settle," and are at variance 
with the suggestion I have proposed. In the cases to 
which my explanation refers there is no settlement on 
the bar of sand, or other material carried down by the 
river. Neither is It necessary to the formation of a bar 
that there should be "a place where the river and sea 
meet with equal force," so as to cause sand held in 
suspension to settle. For, according to my explanation, 
a sear-bar would be formed aliiiough the outgoing current 
held not one particle of matter in suspension, ita only 
effect being to scour away what the waves have thrown 
up. 



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"sra-pboper" compartment op bivers. 271 

Aiber having given much attention to the subject of CoadiUmM 
the Band-baxs which encumber most of the tidal harbours sud-bu* *» 
of the siiorefl of Britain, I proposed, in the Encyclopisdia "^ 
Britannica, the foUo'ning as the conditions under which 
all such accumulations are formed : — 

Ist, The presence of sand or shingle, or other easily 
moved material ; 

2d, Water of a depth so limited that the waves during 
storms may act on the bottom ; and 

3d, Sttch an exposure as shall allow of waves being 
generated of sufficient size to operate on (Ae submerged 
materials. 

In confirmation of this opinion, I maj once more refer 
to the Dornoch Firth. The Oykell, as has been shown in 
ChaptCT IIX, joins it at a point about a mile below Bonar 
Bridge, but we find no indication of what may be termed 
a bar throughout tiie whole of the sheltered part of the 
firth, which extends for 12 miles seaward of that point, 
until we reach the outer portion, where, open to the 
whole fetch of tiie Moray Firtii, there are generated 
waves of sufficient size to act on the materials of which 
the bottom is composed, and we find an extensive sand- 
bank, forming, as it were, a continuation of the shore on 
either side, and stretching quite across the mouth of the 
firth, with the bar in tiie centre of it. 

The same reasoning may explain why, ia such a case buIgm Ajm. 
as the Firth of Forth, for example, no bar ezista The 
Firth of Forth is an inlet or arm of the sea of great width 
and depth ; the seas entering it do not act on the bottinn 
so as to disturb and heap up the matenal of which it is 



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272 INLAND NAVIGATION. 

composed, in the same manner aa in a shallow sea. This 
great natural depth continues as the Forth gradually 
contracts; and before the necessary conditions fra: the 
formation of a bar occur, namely, shallow vrB.teir and 
presence of sand or other easily moved material, tfae 
sea is so land-locked that waves of sufficient size to 
produce the necessary effect camiot be generated. There 
is, in £tct, in the Forth that gradual diminution of depth 
and tTicrease of Midler whu^ combine to produce the 
f^ienomenon of a river vnthout a bar. 

It ifl very interesting to know that Mr. George 
Bobertson, in his recent survey of Indian harbours,' 
found that at Cochin the removal of certain projecting 
spits of sand which protected the bar had aensibly re- 
duced the depth of water, as ascertained by actual sur- 
v^, thus affecting, by the operation of changee wrought 
by nature, a striking proof of the soundness of the con- 
dition which I "have specified as being necessaiy to the 
formation of a bar. Keporting on Cochin, he says, — 
"Were the current kept together till it got into such 
a depth of water that the action of the waves was not 
sufficiently poweriul to stir up the bottom, there would 
be no decided bar. The same result woidd happen were 
tlie current to dischaxge under shelter from the waves ; 
as, for instance, in a land-locked estuaiy. In the survey 
of 1835, when the current was kept longer together by 
more projecting fau^xs terrcB, and by hard sand-banks, 
which prevented the stream from spreading, there were 

> Repoita to tbe OovemBent of Indlk on lodum Hubotin, by George Bobert- 
son, CivU E^igineer, 1871. 



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"SBA-FBOI^R COHPABTUENT OF RITEBS. 273 

16 to 17 feet on the bar. Since then, the fauces terrm 
have been gradually eaten away by encroachments of the 
&ea ; and the survey of 1852 showa that a bar was be- 
ginning to form with only 13 feet on it. In 1858 the 
bar had completely formed, but was veiy narrow. These 
surveys illustrate the true theory of the formation of bars 
at river mouths more beautifully than any set of surveys 
with which I am acquainted ; for it seldom happens that 
the fauces terrce of a river are so much eaten away, and 
the results of their diminution so plain." 

A strong argiunent in fevour of the explanation iBmihJimrert 
have proposed is to be found in the fact that these bars seu. 
are invariably in their shallowest state after heavy seas. 
This view Is also bome out by the material of which they 
are composed. I have examined with care the deposit 
at the mouths of many such estuaries, and I have in- 
variably found that the bar and outer banks consisted of 
coarse-grained sand, without a particle of alluvial matter, 
which, as I shall have occasion afterwards to notice, is 
confined to the inner bed and banks of the river. 

Indeed, when it is kept in view that the river water 
floatfl on the heavier salt water of the sea, and that the 
current on the bar is invariably stronger than on the 
shallow sand-banks on either side, it is impossible that 
the light matters held in suspension by the river can 
" settle down " or " deposit " on the bar. On the con- 
trary, they are swept out by the rapid ebb current, and, 
as has been already mentioned, can often be traced for a 
considerable distance out to sea. 



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274 INLAND NAVIGATION. 

ezperimenta at the mouth of the Wear, to aaeertain 
whence the material dredged fiom and deposited on the 
bar had been brought. The dredgings consisted of sharp, 
gritty sand, brickbats, chalk, flints, pebbles, and marly 
rock materials, precisely of the same character aa had 
been deposited on the beach adjoining the entrance to the 
harbour. In order to test this, a number of small billets 
of wood loaded with lead were deposited at various 
points, and these were gradually moved by the action of 
the waves towards the harbour's mouth, and Mr. Meik 
states that there is only one inference to be drawn from 
the experiment, and that is, " that by the agency of the 
flood-tide, ballast and other material has been swept irom 
the east foreshore of the south dock to the harbour 
mouth, and there settled in the deep water channel, to 
the prejudice of the bar." 

In open bays, in extreme exposures, such, for example, 
as Wick in Caithness, no indication is to be foimd of a 
sand-bank across its mouth, the violence of, the waves 
prevents its formation, and the whole bottom of tiie bay 
becomes a submerged beach. 
ra From -^hat has been said, the reader will at once see 
that the depth of water on such bars aa are caused by 
the waves of the sea, is due to the scour produced by 
the tidal currents, which cross them four times in every 
twenty-four hours. These two agenta, the waves and 
the tidal scour, are constantly opposed the one to the 
other, and the general principles which should guide the 
engineer in all designs for increasing, or even maintaining, 
the depth upon sea-bars, ig the preservation of a sufB- 



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"SEA-PBOPEB OOMPABIMENT OF HIVEHa. 275 

cient amount of tidal water to counteract the tendency of 
tlie sea to heap up detritus at the mouths of our harbours. 

That the beds of the upper parta of rivers are scoured, 
and their depth maintained by the flow of the freah- 
water stream, is not to be questioned; and it is also 
beyond doubt, that in many situations the upper portions 
of the tidal compartments of rivers are kept open in a 
great measure by the Jr&^ioaier stream, as shown at 
page 192 ; but it seems to me to be no less certain that 
the opinions which woidd assign the depth of water in 
the lower parts of tidal rivers, and also through estuaries, 
to any other cause than the action of tidal water as the 
chief agent, are erroneous. In proof of this, I think, I 
have only to refer to some of the investigations which have 
from time to time been made to ascertain the amoimt of 
the river or fresh water, as compared to the volume of the 
tidal water of some of our firths and estuaries. 

By means of a series of careful observations and comF>TiK>n of 
measurements made at the Cromarty Firth in 1837,.tOi,ItLin 
which reference has already been made, Mr. Alan Stevenson 
found that the river Conon, when highly flooded (a state 
of matters which of course occurs only occasionally), dis- 
chaj^es diiring twelve hours a quantity which is only equal 
to -jV*^ P*"* of the water which passes out of the firth at 
every ordinary spring-tide, and -^ih of that which passes 
out at neap-tides. In its summer-water state, the produce 
of the river is reduced to xi?n: ^^ ^^ discharge of the 
firth in spring, and ^^ of the discharge in neap-tides ; a 
quantity too small to affect appreciably either the velocity 
of the currents of the firth or their scouring power. It 



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276 INLAND NAVIGATION. 

has often been argued, that in situations where the velo- 
city of the ebb exceeds that of the flood-tide, the excess 
is due to the increased quantity of water passing out with 
the ebb, the volume of the ebbing waters being assumed 
to be augmented by the amount discharged by the river. 
But this is whoUy disproved in the case of the Cromarty 
Firth ; for while the increased quantity due to the river 
is seen to be only from y^ to tWti *^® average velocity 
of the flood-tide at that place was found to be 2'9 miles 
per hour, while that of the ebb was 3"6 ; an increase 
which is in all probability due to the tide beyond the 
Suters idling more rapidly than it rises, and thus ptt)- 
ducing a greater head and more rapid current on the ebb, 
or to some action of the under-currents which have been 
stated to exist there, but is assuredly not due to any 
augmentation of water from the discharge of the Conon. 
The Tay presents another example of the disproportion 
between the tidal and river waters. That river, as gauged 
by Mr, Leahe when in flood, was found, including the 
Earn, to discharge 969,340 cubic feet per minute. Mr. 
Walter, in his Eeport to the Trustees of Dundee Har*' 
bour, assumes the discharge in round numbers at one 
million cubic feet per minute, or 240,000,000 during four 
hours, and arrives at the following conclusion ; — " To 
compare the above with the effect of the tidal water at 
Dundee, I assume 15,000 acres as the average area (above 
Dundee) of the reservoir or estuary during the first four 
hours of the ebbing tide, and the vertical fall of tide 
during these four hours to be U feet. This wiU give 
7,187,400,000 cubic feet, or thirty times the 240 miUions 



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"SEA-PBOPER" OOMPABTftDSafT OF RIVEHS. 277 

of river water. To compare the ^ect upon the bar, the 
area of the river between Dundee and the bar must be 
added ; and the tidal wat^ upon the bar will be up^^uds 
of forty times the river water," and this, it should have 
been added, only at the exceptional times when the rivers 
are in high flood. One other example may be g^ven to 
show the disproportion between the areas of the inner 
and outer channela. At the Dornoch Firth the high 
water area of the channd, at Bonar Bridge, is 459 square 
yards; at Heikleferry it is 9047, and opposite Whitness 
Poiat it is 25,183 square yards, being fifty-five times 
greater than at Bonar Bridge. 

Backwater. 
But to the eflfect of the sea-waves to collect, and 
the tidal scour to remove, sand-banks, may be traced 
the ori^ of a very important question, which has 
occasioned much discussion and difference of opinion 
among en^neers, and may be stated as follows : — 
Within the bars of all rivers or firths there is a certain 
expjuise or area over which there flows at every tide 
an amount of tide-water measured by the extent of 
the area, and the depth to which it is overflowed. The 
water so impounded at high-tide is what is caUed " back- 
water," a term due, no doubt, to its passing back to the 
sea over the bar, and the question to which I have alluded 
as having so much engaged the attention of engineers, is, 
how fer this area occupied by backwater may be en- 
croached on by sohd works displacing the water, wiiJiout 
injiuiouBly affecting its scouring power on the bar and 



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water may ba 



278 INLAND NAVIGATION. 

lower reaches of the river. At first sight it might seem 
safe to pronounce that no occupation of tide-covered space 
can be made -without prejudicially affecting the scour, but 
after a little more inquiry we shall see that this is not 
strictly the case. 
DKfeTMt Now this question of backwater presents itaelf to the 

ww^toik-' endear in veiy different aspects, as modified by the 
varying physical features of different localities, and per- 
haps, in treating of it, I shall most satis&ctorily illustrate 
ite bearing on navigation by referring briefly to some con- 
troverted cases in actual practice, which were argued 
wholly on the question as to whether, in consequraice 
of certain works, and under certain physical conditions, 
backwater might be excluded without prejudicially less- 
ening the scouring power. The cases selected illustrate, 
to a certain extent at least, the different aspects und^ 
which the engineer may be called on to view tihe question, 
Emd I do not doubt that other illustrations wiU occur to 
other engineers, foxmded on their own experience. 

The first example to which I shall refer is Hartlepool. 
Immediately above the harbour there is a tide-covered 
area of 173 acres, called the " Slake," communicating with 
tixe harbour by a narrow entrance. The whole of the 
water, which at every flood-tide pours into, and at every 
ebb flows out of, ^m vast natural basin, passes over and 
scours the sea-entrance into the harbour of Old Hartle- 
pool The harbour authorities placed gates across the 
entrance to the Slake, and, in order to render the scour 
more effective, impounded the water at high-tide, and at 
low water allowed it to escape through large sluices 



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"sea-pkopee" compabtsient of RIVEHS. 279 

formed in the gates so as to act upon the harbour between 
half-ebb and low water, at which period the scour is found 
to be moat eflScacious. A proposal was made by a com- 
pany seeking powers imder an Act of Parliament to 
enclose a portion of the area of the Slake, and I was 
appointed to report to the Admiralty on the propriety of 
sanctioning the encroachment. After full inquiry I had 
no difficulty in advising that the proposed encroachment 
would decrease the scouring power, because it was proved 
in evidence that when the gates were left open the high- 
water mark in the Slake, and that in the outer harbour 
beyond the sluices, attained exactly the same level, show- 
ing that the baeia was not too large to contain all the 
water that could be supplied by t^e flowing tide, and 
therefore, that it was not safe for the Harbour Trustees to 
part with any portion of the tide-covered area. The 
eflect of closing the tide-gates ^d permitting the Slake 
to be filled by the sluices was also stated in evidence, and 
the result is interesting and important. It appears that 
when the tidal flow into the Slake is checked by shutting 
the gatee, and the only supply is made to pass through 
the sluices, their water-way is not sufficient to fill the 
basin, and the high-water level does not, in that case, 
reach within four inches of the natural tidal range out- 
side, 80 that a quantity of water, amounting to upwards 
of 90,000 cubic yards, is excluded when the Slake is filled 
throogh the sluices. 

The other case to which I shall refer is the tidal basin At uontraM 
at Montn»e, which vrill be found to present a totally dif- 
ferent tidal action. The basin at Montrose has an area 



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280 INLAND NAVIGATION. 

of 1200 acres, and, like that at Hartlepool, is a natural 
reservoir which scours the sea-«haiinel of the harbour. 
From caxe&l obBervations made by Mr. George Buchanan, 
it was found that on an average of tides the high water 
in the basin is upwards of 9 inches below the level of the 
high water outside, indicating that the flood-tide does not 
flow sufficiently long to fill the basin ; and from this fact 
it was assumed that a proposed embankment, which had 
the effect of reducing the area of the basin, might be 
sanctioned without injury to the scour, as the only result 
would be to cause the water displaced by the embank^ 
ment to spread itself over the surfece of the basin, slightly 
raising its level, and thus compensating for the portion 
abstracted. With reference to a portion of the water this 
is no doubt true, but it would not be safe to carry this 
assumption beyond a certain limit, for, as su^ested by 
Mr. Buchanan, though the level of the vmter in the 
basin be raised by water which formerly occupied the 
space enclosed by the embankment, it must not be over- 
looked that the velocity of the current flowing into the 
basin will be reduced in proportion to the reduction of 
head between the sur&ces of the water within and without 
the basin, so that the abstraction of backwater in such a 
case must depend on whether there be time for the basin 
to fill with the reduced head. 

Hartlepool ajid Montrose are basins into which, as I 
have explained, the sea ebbs and flows ; but there are 
other casea connected with tidal rivers in which the 
" backwater " question forms an important element : for 
example, Birkenhead Dock on the Meraey. The scheme 



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"BEA-PROPER COMPARTMENT OP RIVEBa 281 

for that work, designed by tlie late Mr. J. M. Bendel, 
contemplated a diaplacement of 3,750,000 cubic yards of 
tide-water from Wallasey Pool opposite Liverpool, cover- 
ing an area of nearly 300 acres. This was opposed by the 
Liverpool Bock CommiBsion on the alleged injury that 
the abstraction of so much water would produce on the 
bar. The promoters of the Wallasey Fool scheme con- 
■ tended that no abstraction of water would take place in 
consequence of the wall they propc^ed to erect sxToea the 
mouth of Wallasey Fool, and averred that the water which 
formerly flowed into the pool woidd, after the erection of 
the wall, flow into the upper part of the river, and be as 
eflFective as ever in scouring the bar. This averment was 
based on the result of tidal observations which showed 
that the wide expanse caused by Wallasey Pool produced 
a decrease in the velocity of the tidal currraits, and a 
depression in tlie level of the water opposite the pool. 
The observations also showed that, notwithstanding the 
disturbance of tidal flow caused by Wallas^ Pool, the 
water moved up the estuary with a momentum which 
nused the level of high water at all the stations in the 
upper part of the river. Thus taking Princes Basin, 
nearly opposite Wallasey, as zero, the means of the heights 
of spring and neap tides at difierent points were as fol- 
lows : H«Wt »t Bprlngfc Holebt at Nei]«. 



Princes Baain, . 


Balowun. 
Ft In. 




Btinrnit 
Ft. In. 



EUesmere Port, . 
Euncorn, . 


1 1 
1 1 


6 
11 


Fidlers-ferry, 
Warrington, 


.18 
..33 


10 

1 6 



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282 INLAND NAVIGATION. 

It further appeared from calculation t^t the raising 
of the level of that part of the estuary which lies above 
Wallasey Pool to the extent of ri4 inch would give an 
' amount of water equal to the whole quantity displaced by 
the closing of the pool Aftet* considering all tlie data 
adduced, I came to the conclusion arrived at by Mr. 
Eondel and the other engineers who supported the Bill, 
that the wall, if built in the line proposed, would r^^ulate 
the current, restore the lost momentum opposite to the 
pool, and cause more water to pass into the upper reaches 
of the river, and ihsA on the whole the scour on the bar 
would not be appreciably affected. After a contention of 
twenty-four days before Committees of both Houses of 
Parliament in 1844, tiie Bill was passed, and the wall has 
since been made, and Mr. Lyster, ihe present engineer to 
the Liverpool Dock Commission says — " The abstraction 
of water by the construdion of the Birkenhead Docks 
had had no effect upon the bar of the Mersey, although 
at one time it was thought that the loss of so consider- 
able an amount of water as that jfrom Wallasey Creek 
would affect the condition of the entrance channds to the 
river, but the depth over the bar remained the same as it 
Tras fourteen or fifteen years ago."' 
Level u which AnotJier important question as affects scour is the 
■betnoted. lovol at which " backwater" is abstracted. The abstrac- 
tion of water jfrom a marsh on a high level covered only 
at high spring-tides is very different from abstracting an 
equal amount of water from a space which is filled by 
every tide. 

* Jfimife* qf Proeetdingt t^ On Inttitutim qf CisU Bngtneert, toL zzvL p. 423. 



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"BEA-PROPER" COMPAKTMENT op RIVEBa 283 

It will readily be seen that the efficiency as a scour of 
a cubic yard of water filled and emptied by every tide, as 
compared with that of a cubic yard filled onij^ve times 
during every set of spriTtg-tides, ia in the ratio of 730 to 
144, not to mention \h.e more effective scouring power 
of water diBcharged iJter half-ebb, as compared to a 
similar quantity discharged, for example, during the first 
hour after high water. 

The value of the water as a scour is therefore influ- 
enced both by ite volume and by its level, and may be 
expressed as follows ; — 

S ocTT, 
where V = the volume or cubic feet of water space above the low- 
water level of the estuary. 
T =3 the number of times it is filled by the tide throughout 

\3i6 year. 
S = the effective Hcouiing power. 

The only other consideration that should be kept in 
view is that of two spacea, V, V, of equal capacity, and 
filled every tide, that which is lowest in position will be 
moat effective in operating on the low-water channel. 
These values must of course be held applicable only to 
different conditions of the aame river where the hardness 
of the bottom to be scoured and other circumstances 
remain unaltered. 

The different exMuples I have given will serve to 
illustrate the general principles on which almost all 
"backwater" questions are treated, and fi*om what has 
been said it will be apparent that evety new case 
that occurs must be regarded with a special view to 
its own distinctive features, as suggested by physical 



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poaitioDi 



284 INLAND NATIQATION. 

elements peculiar to each locality, such as the configura- 
tioa of the banks and bed of the estuaiy, the simultaiieous 
levels of the sur&ce of the water at different periods of 
the tide throughout the estuary, the velocities of the 
surface and under currents at different periods of tide and 
the times of ebbing and flowing, together with many 
other more minute data peculiar to each case, which it is 
not possible to specify in a general simmiary. 
oeoerai pro- Perhaps, however, the following general propositions, 

ngRidingbMk- '^ ^ot in all cases applicable, may nevertheless be held 
to represent pretty accurately our general knowledge as 
regards " backwater :" — 

1. The depth on Bars is due to backwater. 

2. Wiere- the high-water level of the surface of the 
river, estuary, or haMn is the same as, or higher' than, the 
level seaward of the poirU of abstraction, a dimintition of 
tide-covered area will reduce the effective backtcater. 

3. Where the highrwater level of the surface in the 
river, estuary, or basin is lower than the level seaward of 
the point of abstraction, a diminution of tide-covered area 
may, in some cases, he made without reducing the effective 
backwater. 

4. The lower the levd of backwater the greater will be 
its effect in scouring the low-water cha/nnel, and, ther^ore, 
the nearer the site of abstraction is to high-water mark the 
less injurious will be the effect. 

5. By enlarging the tidal capacity of a river at a low 
level, where the acquired volume is filed every tide, com- 
pensation may be given for a much larger amount of 
water excluded at a higher level 



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" SEA-PROraat " COMPABTMENT OF BTVERS. 285 

6. In consequence of the disturbing effects of the waves 
of^ sea, the large discharge of rivers during high floods, 
and the varying nature of the beds of estuaries and bars, 
it is not possible to conclude that vnth a given quantity of 
backwater, as deduced from the measurement of the tidal 
capacity of an esAuary, a condant 7tavigcd>le depth can be 
maintained over the ba/r. 

In many of the navigable rivers in this countiy, such Lower puts or 
as the Mersey, the Ribble, or the Tay, the lower part u th* ueney, 
of the estxmry presents the feature of large tracts ofiDii^ednniem 
sand-banks, some covered to a small depth and others* '^^ 
drying at low crater, and the bar, which we have been 
considering, is situated ikr to seaward — at the very out- 
skirts, if I may so express it, of these accumulations. 
It is not a litUe remarkable t^t in such circum- 
stances the position of the bar and the depth of water 
upon it, though varying from time to time, as affected 
alternately by summer calma and winter storms, should 
on the whole maintain for years, if not the same position, 
at least pretty much the same average depth of water, 
and, indeed, that the variation either in position or depth 
should not be such as materially to incommode navigation, 
much less to close the access to the harbour. We find, 
for example, that the entrances to Liverpool, Dundee, and ■ 
many smaller harbours, although across bars and through 
extensive sand-banks, have always had a pretty uniform 
depth maintained by the bcout of the backwater which 
keeps the channels open. 

Little has been attempted to improve the entrance to 
such estuaries by artificial works, partly no doubt from 



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286 INLAND NAVIGATION. 

the great expense that would attend asij such operation, 
fUld partly on account of the difficulty in predicting 
what effect auch works might have on the tidal ciurents, 
in situations bo esposed to the sea, and how &r any 
interference with their flow might prove beneficial or 
detrimentaL The tendency has rather been in such large 
estuaries to trust to the natural scour of the tidal waters, 
and by careful lighting and buoying to indicate to vessels 
the navigable track by following which the mariner will 
find sufficient water at the proper time of tide to float his 
vessel over the bar and carry her to her destination. 
cbiuBtB on The ciianges wJbidi take place in the sand-banks and 

Tt,y. bars of such estuaries as those to which I have been re- 

ferring are capricious, and in many cases unaccountabla 
For example, it is shown by existing surveys that the 
position of the bar at the mouth of the Tay was the same 
in 1689, 1816, 1833, and 1846; but a survey made in 
1858 showed that it had shifted a little to the north, and 
what was &om the earliest times known as the navigable 
channel no longer had the deepest water. Throughout 
all the periods mentioned, however, the bar had, and 
still has, a navigable depth ibr the largest vessels. 
At u>e vmej. At the Mersey tbe changes in the position of the bar 
have been more fiequent, but fixim observations made by 
Captain HUls, the Marine Surveyor to tiie port, it does not- 
appear that they have been accompanied by any permanent 
diminution of average navigable depth, nor, indeed, by any 
change in the 'general level or area of sands dry at low 
watar, or in the tidal phenomena of the estuary. What 
was called " The New Channel " of the Mersey, discovered 



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"bea-peopee" covpastvest of rivers. 287 

in 1833, continued navigable for ax years, and witihin 
eight years of its discoveiy became obliterated. The 
second, or "Victoria CSiannel," was buoyed in 1839, and 
after gradual deterioration was disused in 1857, and 
superseded by the " Queen's Channel" Referring to 
observations on the banks and tides, Captain Hills states 
the area of sand-banks dry at low water as follows: — 
Iq 1736-6, . . . = 27-97 sqnaie milea. 
„ 1833-5, . . . = 27-82 „ 
„ 1857, . : . = 2706 „ 

The mean height of high water above the Old Dock 
Sill he found to be as follows : — 

1st. Mean HeiglU of High Water tkrmtghout the Year. 

No. or Udes 



1768, 


16-610 feet above 0. D. S. 


703 


1769, 


16-362 


706 


1770, 


16-605 


706 


Mean of 3 years, . 


16-469 




1864, 


16-426 feet abere 0. D. S. 


663 


1866, 


16-426 


678 


1866, 


16-616 


661 


Mean of 3 yeara, . 


16-464 




2d. ifean Lead o/ Kighegt Sprin^-tida throughout the 


Tar. 


1768, 


18-690 feet above 0. D. S. 




1769, 


18-673 




1770, 


18-816 




Mean of 3 years, . 


18-693 




1861, 


19-030 feet above 0. J>. S. 




1866, 


18-873 




1866, 


19-236 




Mean of 3 yeara, . 


19-016 





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288 INLAND NATIOATION. 

" The conclusioDfi flowing from a comparison of tidal 
levels, coincide with those deduced from the measurement 
of areas, and go to establish the &ct which, at first sight, 
seems at Tariance with .every-day experience, viz., that 
the sands of the bay in two respects, area and elevation, 
present evidence of only trifling change, bo trifling that 
from the data given, it would be difficult to pronounce 
whether they were on the iacrease or decrease." 

Captain HiUs has suggested that there may be a 
regtdar " cyde of rotation " in the changes that are going 
on in the Meniey, but time alone can prove whether such 
be the case. The bar of the Tay seems hitherto to have 
been less variable. Such changes may be due to certain 
states of prevailing winds during high tides, and even to 
the grounding of vessels in the channel The alteration 
ill the bar of the Tay was attributed by seamen to the 
loss of a large vessel laden with jute. The efiect of such 
an obstruction as a stranded vessel, in causinig the cur- 
rents to act on the bottom, has been already refeired to 
at page 178, where it was seen that even the bed of the 
Tay, consisting of heavy gravel, vras materially altered in 
the course of a few tides, and how much greater must be 
the efiect of a vessel's hull swept by the curraits of flood 
and ebb on the soft sand-banks in the estuaries of which 
we have been speaking. It Is well known that vessels 
grounding on such sand-banks sometimes entirely dis- 
appear in the course of a few tides, the opposition they 
offer to the currents causing a scour which veiy speedily 
excavates a hole large enough to bury them out of sight. 

t Hills'a Hgdrogra^y of the Sfereej/ Ettitary, Lirerpuol, 186S. 



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"sea-pbopeb" cohfaatuent of bitebs. 289 

Captain Hills mentions two such cases liaving occurred 
on the Mersej. Now, were we to suppose a vessel 
grounding even for a tide on the edge of a bank forming 
one side of the bar or deep channel of such an estuary, it 
is quite possible that this, in connexion with some par- 
ticular state of the winds and tides, might so affect the 
banks as to give the current, and ultimately the navigable 
channel, a tendency to shift, which succeeding disturbancee 
might so encourage and increase as ultinmtely materially 
to alter the navigable track. Dock and other works are 
also being formed on the estuary, both of the Mersey and 
Tay, which, though not decreasing the depth, may pos- 
sibly so a£fect the out^owing currents, as, in combination 
with certain states of wind and tide, to have some effect 
in varying the courses of tJie outer ehannela 

To trace all the movements of the channels and banks 
of open estuaries to their true origin would indeed be 
hopeless, for winds and floods, as well aa stranded vessels, 
may each or all have their share in giving a current a 
slight direction, which, once commraiced, may terminate 
in a new channel and newly formed sand-banks. As an 
example of tiie strange fireaks, if I may so express it, 
that are to be met with in the movements of banks, I 
may refer to a case on the Tay, where a sand-bank, in 
the course of a single year, changed its position without 
altering its form. Fig. 58 shows the part of the estuary 
of the Tay, opposite Balmbreich Castie, where this 
occurred. In surveying the river in 1833, the bank was 
foimd to have the outline and occupy the pofdtian shown 
in dotted lines. In 1834, on reeuming the survey, tiie 



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INLAND NAVraATION. 



position of the bank was found to be altered. It had 
retained nearly the same outline, but had shifted about 




700 feet iurther up the estuary, and occupied the position 
shown in hard lines. I never met with so striking an 
instance of what I may term altered strength of tidal 
currents without alteration of their direction; for I 
believe the general movement of the particlea of sand 
composing the bank was caused by decreased power due 
to little raiQ-&ll, whUe nothing had occurred to alter the 
direction of the currents, so that the particles of sand 
were carried forward in the direction of the flood current, 
and deposited so as to present nearly the same outline as 
shown in the illustration. 

The Wear. 
B&nornch Some of our rivers, however, such as the Wear and 

WewandthB the Tyne, have not much of what may be termed the 
impro^^'by cstuarial features, and require different treatment The 
p™ spisra- construction of piers for improving the entrances to 
such rivers is often highly beneficial. I shall take as 
an example the Wear, which is shown in fig. 59. In 



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" SEA PROPER " COMPARTMENT OP RIVERa 291 

its natural state, such a river as the Wear flows across 
the beach &om high to low water, in a broad and 
Bhaliow channel, the direction of which is ever chang- 
ing. It thus forms a long bar or shoal, with broken 



AT LDV WTEn 






water throughout its whole extent. But the pro- 
jection of piers across the beach affords shelter from 
the waves, and admits of a navigable channel being ex- 



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292 ISLAKD HATIOATION. 

cavated and maintained ; and afler a veasel entering the 
river crosses the short bar, which occurs at or near the 
pier-heads, she not only gets into deeper -water, but has 
the additional advantage arising &om the shelter afforded 
by the piers. To this extent piers in such situations are 
highly advantageous. They further act beneficially in 
directing the flow of t^e tidal currents in a fixed diannel 
across iJie beach, and, in connexion wit^ an increase of 
tidal capacity in the interior, such as I have mentioned 
as the result of tiie works on some rivers, they cannot 
fitil, if judiciously desogned, to operate braieficially, by 
THMntaining an increased depth of water on the bar. 
Founding on these views, when consulted in 1858 by 
the Commissioners of the river Wear, as to the best 
means of permanently deepening the bar which extends 
between the heads of Sunderland piers, Messrs. D. and 
T. Stevenson recommended the construction of covering 
piers, as shown in dotted lines, with an entrance 1200 feet 
seaward of the present pier-heads, and described their 
action on the entrance to the river in the following ex- 
tracta: — 

" Protection fix>m the action of the sea, and increase 
of backwater, are the means of operating effectually in 
keeping down the bar of the Wear. The effect of in- 
creased backwater, due to the improvement of the river, 
would imdoubtedlj, as stated in former reporis, act very 
beneficially. But nevertheless, so long as iiie bar is ex- 
posed to the tmdiminished action of the sea during heavy 
gales, it must be subject to constant changes in its depth 
of water ; and this variableness in the navigable chaimd. 



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" SEA PROPER " COMPARTMENT OP RIVERS. 293 

espedally with the larger draught of vessels to be now 
accommodated, must doubtless be attended vith incon- 
venience and obstruction to the trade of the port, which 
it is most desirable to avoid. We have therefore con- 
sidered it necessary to submit to the Commiflsioneni a 
plan of improvement based on the fundamental principle 
of protecting the bar from the tendency to heap up or 
accumulate during heavy seas. . . . We may state gener- 
ally that the effect of these piers will be to protect the 
entrance to the harbour, and to allow the tidal scour to 
act fred.y on the bottom, and maintain a greater depth on 
tbe bar, while the deeper water in which the pier-heads 
are proposed to be ibunded, wUl prevent the bottom at 
the outer entrance from accmnulatiog or rising, so as to - 
act as an obetniction to such Tessels as tJie interior of the 
harbour is capable of accommodating." 

There are, however, rivers whidi present very different bk of the 
characteristics from those we have been consideiing, both 
as regards the fresh-water stream and the action of the 
sea, and it will be interesting to notice them ; I allude to 
such livers as the Misedssippi and the Danube. 

Mr. Ellet, though founding his views on totally dif- 
ferent premises from those I have laid down, also comes 
to the conclusion that the bars of the Mississippi are 
not due to the materials deposited by the out-going 
stream. But I shall give his interesting explanation in 
his own words. I have, however, no information to 
enable me to form an opinion as to its correctnesa It 
is based on the &ct already described in Chapter V., 
that at the junction of a river with the sea, the fresh 



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294 INLAND NAViaATION. 

water flows in a stratum above, and distinct from, the 
salt water, for some distance after entering the oceaa 

Founding on this, Mr. Ellet says, — " The velocity of 
the river is not destroyed, nor veiy sensibly diminished, 
at t^e bars. When the river was rising, but still Sax 
from being at full height, I measured the velocity of the 
current on the bar of the Pass h la Loutra, and found it 
to vary, at different times and places, from 3 feet to 3^ 
feet per second, or from 2 miles to 2]^th miles per hour. 
I measured it also repeatedly on the south-west bar, and 
foimd it there 3 feet per second, or about 2 miles per hour. 
But there are many parts of the river where the speed 
of the current does not exceed 2i^ miles, or even 2 miles 
per hour, lq times of flood, and where it is, notwith- 
standing, more than 100 feet deep. In feet, on testing 
the velocity of the south-west pass, 4 miles above tiie 
bar, and in 5 fethoms water, I found the current to be 
but 2 miles per hour, — precisely the same as it was 
under like circumstances of wind and tide on the bar. 
Tlie current of the Mississippi sweeps over the bars at the 
mouths of the passes, and at periods of flood many miles 
out into the gulf, with a velocity almost undiminished 
by its contact with the waters of the gul£" " The river 
water does not mix suddenly with the sea, but rises upon 
it, floats over it, and rushes fer out into the gulf on the 
top of the dense sea water, by which it is buoyed up. 
I tested this repeatedly, and found uniformly a column of 
fresh water, nearly 7 feet deep, in the gulf, entirely out- 
cdde of the land, and salt water at a depth of 8 feet from 
the surfece, and extending thence to the bottom. The 



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" SEA-PROPER " COMPARTMENT OF RIVERS. 295 

river does not come down with a certain normal depth 
and speed, and encounter the gulf at the bar. Ko such 
process takes place. Hiere is no sudden destruction of 
velocity, or consequent deposit of suspended sUt. But 
the water of the Mississippi does not move over the sur- 
&ce of the gulf at a speed of 3 feet per second without 
imparting a portion of its motion to the sea.* The fresh 
water and the salt water take the same direction towards 
the sea, and with nearly the same velocity, hut yet keep 
separate. This state of things clearly cannot eiist at the 
bottom ; for aa the river water is for ever coming for- 
ward, if the salt water all flowed towards the gulf, it 
would all be carried out, and river water woidd take its 
place. Salt water must come in from some quarter, to 
supply the current of sea water that is for ever setting 
towards the gulf, beneath the water discharged by the 
river. This salt water can only come from the sea, and 
can only come in along the bottom. It is, in feet, an 
eddy that is here at work, the movements being in a 
vertical instead of a horizontal plane. Now, the ques- 
tion is. How does this account for the existence of the * 
bar? The fi^sh water running out cannot produce de- 
posit, for it has velocity enough to sweep away a foun- 
dation of coarse gravel The outpouring salt water 
immediately beneath the fresh, cannot produce deposit, 
because it also has a velodty seaward strong enough to 
remove auytliing that is brought down the Mississippi. 
The salt water that is coming in might produce, and I 

' Thia ii in harmony with Ventnri'i weU-known erperimenta, from which he 
found, that a body of water in motion leads or drags with it the particlea of 
water at r«at with which it may be in contact 



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296 INLAND NAVIGATION. 

doubt not does produce, a depcsit, for it passes oTer the 
soft muddy bottom of the gulf, and moves into the river, 
and along the bar, at a veiy alow rate. According to 
these &cts, and this reasoning, there must be usually on 
the bar three distioct strata : Ist, Fresh water, running 
out at top, found by experiment on the s.w. bar to have 
a velodty of 3 feet per second. 2d, Salt water below the 
fresh, also running out with nearly the same vdodty as 
at top ; and Sd, Salt water coming in slowly along the 
bottom, and apparently a sheet of salt water between 
that running out and that coming in, whic^ will be with- 
out motion. 

" But as already said, and as is obvious, all ihe sea 
water that comes in must go out again. It comes in 
along the bottom, and it must go out between tlie column 
of salt water coming in and that of the fresh water going 
out. Each particle of salt water, therefore, must change 
its direction and position in devation. It must pass from 
an inward-bound lower stratum to an outward-bound 
upper stratum. But in passing through this change of 
motion, its velodty up stjream must be neutmlized. It 
passes, to use a technical term, the dead point. At this 
point it may cease to bear its whole burden of mud, 
which it has brought from the gulf fruiher forward. It 
leaves it, or a portion of it, at the turning-point. This 
turning-point is the place where the bar for the time 
being is in process of formation. But as the upper and 
lower strata are moving in opposite directions, the inter- 
mediate column must of necesraty have a rotatoiy motion. 
That motion must be shared by the lower column of salt 



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"S&ArF&aPER COUPABTHENT OF BITEBS. 297 

irater, and Hub tuming-pomt must therefore be formed 
at tKe same time at different places along the har." 

The Danube is interesting aa an example of a large Bar of tbs 
river having been Bucceeefully treated by the construe- ocom, ud 
tion of piers, and also, aa the reader will find, m the origin impraremeat. 
of it« " bar " aa distinguished from the sear-bars treated of 
in the b^;inning of this chapter. 

In 1856 the " European Commission of the Danube" 
was appointed under the Treaty of Paris, and consisted 
of seven delegates, representing England, Austria, France, 
f^iissia, KuBsia, Sardinia, and Turkey, and its object was 
to improve the bar of the river, and open the navigation 
to the traffic of all nations. The Danube, after flowing 
oveff a course of 1700 miles, and draining 300,000 square 
miles of coimtry, enters the Black Sea by three separate 
mouths — ^the northern called the Elilia, the Cfflitral the 
Sulina, and the southern the St George's mouth. The 
first duty of the Commission, with the advice of Sir 
Charles Hartley, who was appointed their engineer, was 
to select one of the three mouths for improvMnent, which 
was by no means an easy taak, as each of them presented 
advantages peculiar to itself, and after much conEoderation 
the Sulina or central channel was selected, and although 
considerable difference of opinion existed as to the pro- 
priety of the choice the result has shown that the cotiise 
adopted was judidous. 

The Danube dischai^;es in ordinary flood no less than 
twenty millions of cubic feet of water per minute, enters 
a tideless sea, and we have a totally difierent class of 
phenomena to deal with fi^>m those of the kind which I 



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298 INLA2n> NAVIGATION. 

hare just been coDBidering. The river brings down an 
unount of detritus which has been ascertained by Sir 
Charles Hartley to be equal to 27 cubic inches per cubic 
yard, and to be eqxial, in cases of high flood, to no less 
tiian 600,000 cubic yards of solid deposit in 24 hours. 
Like the Mississippi and tlie Nile, the Danube owes ita 
extensive delta to the gradual accretion of this sedimen- 
tary deposit, and the bar at its mouth is due to the same 
action. It therefore differs entirely from tiie bars in this 
country, as is well exemplified in the fikct, as has been 
already stated, that, whereas in our harbours the bars are 
always deepest when the sea is calm and the rivers are in 
fiood, and therefore most efficient as scouring agents, at 
the Danube the bar is, on the contrary, invariably s^icH- 
loioest when the liver is in flood, because it is then chai^;ed 
with a larger amoimt of detritus. 

Another feature of difference in the treatment of such 
a case as the Danube is to be found in the circumstance 
that tliere is no reversal of the cturent due to tidal influ- 
ence, and therefore it is unnecessary, in fixing the direc- 
tion of the piers, or indeed in desigmng any of the works, 
to provide for the admission of tidal water to act as a 
scour on its retiun to the ocean, a provision which always 
demands special attention in designing tidal works on our 



The works executed at the Sulina mouth, as shown 
in fig. 60, consist of a north pier 4640 feet in length, and 
a south pier 3000 feet in length, both built of pierres 
perduea surmounted by a timber staging, with an entrance 
between of 600 feet, and the slightness of their structure 



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"SEA-PBOPER" COMPAETtiENT OP RIVERS. 299 

indicates the modified character of the waves to which 
they are exposed. 

The works, which are understood to have cost about 
£100,000, are highly creditable to the talent and energy 




of Sir Charles Hartley, and have now been completed for 
nine years, and their effect has been most satis&ctory, as 
proved by the feet that, previous to dieir construction, 
the depth on the bar never exceeded 11 feet, and fre- 
quently fell to 8 feet ; whereas, according to the last 
accounts from Sir Charles Hartley, the depth for the last 
five years has never been less than 15 feet, and has often 
been as much as 17^ feet. 

It is obvious, however, that as the Danube must con- 
tinue to bring down an enormous mass of detritus, so, in 
course of time the works which have proved so successful 
must be extended — an event which has been fiilly antici- 
pated by its projectors, and in this respect we find an 
interestiog difference between such works as the Danube 
piers and the harbour works o£ this country, for here the 
object being to prevent the waves from acting on the 



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300 INLAND NAVIGATION. 

bottom, the engineer extends his w<n-ks out into a deptli 
of water where there is little or no disturbance of the 
bottom, and if thia is once secured he may calculate on 
the increased depth of water remaining permanent, where- 
as at the Danube the piers must be projected to keep 
pace with i^ gradually increadng delta at the river's 
moutlL 

Habd Babs. 

In other places we find what are termed "hard bars," 
which I have still to notice. For examples of theee I 
refer to such places as Ballyshannon in Ireland, or Loch 
Fleet in Sutherlandahire, both of which I have had 
occasion professionally to examine. The bar at Loch 
Fleet, for example, is composed of boulders firmly im- 
bedded in a mass of indurated gravel, and is obviously a 
continuation of a bed of similar fiirmation which seems 
to traverse the coast at that place, while that at Bally- 
shannon is simply a heap of large bouldera The con- 
sequence, in either case, is that no scoimng power can 
make the least impression on the diannel Such bars are 
entirdy due to the hardness of the bottom,' and though 
their hardness makes such obstructions troublesome to 
remove, and though, moreover, they are generally in 
exposed situations, still they are comparatively easily 
treated by the en^eer, and an encouraging prospect is 
always held out that their removal will be attended with 
permanefU benefit, since by excavating a diannel through 
them we at the same time remove the evil and its cause. 

The entrances to some rivers are greatly impeded 



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" s&a.-f&ofer" oompabtuekt of bitebs. 301 

by shingle or gravel, carried along by the waves from 
the adjoining shores, and deposited in the channd. I 
have knoTm such deposits, if not whoUy removed, at least 
greatly modified by erecting groynes across the beach ia 
such a position (depending on the direction of the heaviest 
seas), as eitiier to collect the shingle and retain it tmtil 
it can be carted away, or to lead it past the harbour 
mouth altogether, and force it onwards to a place of 
deposit in an adjoining part of the coast ; and when this 
can be brought about, the engineer may congratulate 
himself on having deigned a very successful work. 



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CHAPTER XIII. 

RECLAMATION AND PROTECTION OF LAND. 

Scbemea for gaioiDg land and improTing tutvigatioii not genenilly compatible^ 
mastrated bj the Dee— Depression of low-water line apt to mislead, as tcated 
in the Lnna— Increase of tidal water at the Lune, Tay, Mid Ribble, and ila 
effect an a acouring agent — Adjoining property beoefited hf rirer improve- 
menta — Proceu of land-making deiiendi on amount ot matters held in ans- 
penaion — Heaviest matton fonnd next the aea in tidal eatnariea, the reTerae 
in Inch riven aa the Danube, etc. — Size of particlea which eataariei are 
capable of carrying — Weight of different depoiita in tile bed of the Clyde 
— Quantity of matter held in impenaion by different rivets — Fonnation of 
deltas — Level of vegetation in marsh lands — Works for protectjoa of marali 
lands — Works for protection of land in open estnaries. 

Scheme* for SucH twofold Bchemes as liave for their ostenable 

gaining land 

and improTiDg object the improvement of rivers and the formation of 
geneniij com- land, have generally been unauccessiiil in benefiting navi- 
gation. I do not affirm that river works, constructed on 
the principle that has been advocated in the foregoing 
pages, have not the effect of making land, in the par- 
ticular sense in which I shall afterwards explain it ; but 
land-making is no part of sound Siver Engineering. 
Judiciously designed works may, as I propose now to 
show, reclfuim and protect land, while at the same time, 
as their primary object, they improve navigation ; but I 
know of no case where the interests of navigation have 
been promoted by any measure which has for its main 
object the construction of walls designed to convert large 
tracts of tide-covered sands into culti\uted fields. 






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keclamation akd protection op land. 303 

Ejvkb Dee. 

I shall refer to the Dee, in Cheshire, as an aggravated 
instance of the incompatibility of the two interests.' The 
outline of this river is shown in Plate V., from a survey 
by Messrs. Stevenson, made in 1838. The River Dee 
Company, incorporated by Act of Parliament in 1732, 
have frxim time to time reclaimed fr^m the upper part of 
the estuary a lai^ tract of land, extending to about four 
thousand acres, which is now in Ml cultivation; and 
alongside of this gradually gained territory the river has 
been conducted from Chester to near Flint, in a narrow 
canal of about 8 miles in length, and 400 feet in width, 
A considerable portion of land has also been reclaimed on 
the Flintshire side of the estuary, though not by the pro- 
prietors of the Dee Company ; and it is beUeved that the 
segregate amount which has from first to last been gained 
from the sea is about seven thousand acres. Now, it is 
well authenticated that previous to the commencement 
of the land-making operations on that river, there was a 
depth of not less than a &thom at low water of spring- 
tides up as &r as Burtonhead, and that there was an 
anchorage for vessels of the largest size opposite to Park- 
gate, the positions of which places are marked on the 
plan. But when I surveyed the Dee in 1838, the depth 
of 6 feet was not foimd for more than six miles below 
Burtonhead, the low-water features of the estuary having 

' Qrtot Britain Coiuling PUol, by CapUin Qreenville Colliiu, Hjdrognplier 
ID OrdinaiT to the King*! Mort Exodlent Majesty, LondoD, 1767 ; ReporU to tht 
Admiralty, by Captain Wuhington; Report qf Tidal Harbottr Commumontn; 
SepoH hj Mean*. Storeiuoii, 1639. 



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304 IShAm> NATIOATION. 

been forced to that extent farther seawards by ihe ei- 
tensive reclamation of land in the upper part of the estu- 
ary, and the consequent diminution of the tidal scour. It 
cannot, we think, be disputed, that the effect of the works 
executed on the river Dee, whatever may have been the 
anticipations of their projectors, has been to shut out the 
sea, and form land at the expense of the navigation. 

The process followed in carrying out the land-making 
works was to construct a high bank, rising 9 feet above 
the level of high water, so as to confine the river to the 
south ^de of- the estuary. The tidal water, which was 
admitted to flow fireely between the bank and the north 
coast, quickly deposited layer after layer of sand and silt, 
and in &ct shut itself out, and so soon as the sur&ce had 
attained a sufficiently high level, a cross bank was con- 
structed between the main embankment and the north 
shore, and thus the large area shown on the plan was }>it 
by bit reclaimed. The reckiming banks were gradually 
strengthened and pitched on the outer &ce, and sub- 
stantial sluice were formed, which are shut against the 
ingress of the rising tide, but being open at low water, 
eJIow the drainage-water to escape from the reclaimed 
ground, some of whidi is still below the level of high 
water. 

It will at once be seen that the works constructed in 
the process of land-making, as carried out on the Dee, were 
totally different from i^e low-water training walls which 
I have described. The system piirsued is in fiict in direct 
opposition to the principles of Biver Engineering which 
have been laid down, and the result, as has been seen. 



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RECLAUAHON AND PROTECTION OF LAND. 305 

has not been &vouTable to navigation, at all events in 
the case of the Dee. 

But an objection has sometimes been raised to navi- i}«ptchIob oT 
gation works formed on the principles laid down, which it apt to misisMi. 
is necessary to notice. The change produced on the 
relative levels of the low water and the banks, by tiie 
depression of the low-water line, described at page 250, 
have sometimes led to considerable misapprehension. 
This lowering of the surfece of the water when the river 
is confined by walls in the lower part of an estuary, in- 
vaiiably conveys the impression that a great rise has 
taken place in the level of the adjoining sand-banks, and 
it has consequently been thought that the erection of 
river walls is inconsistent with the principle of non- 
exclusion of tide-water which I have been advocating. 
But leaving out of view, for the present, the enormous 
gain to the navigation by the increased scour, due to the 
enlaigement of the channel, as ezpkined at page 224, it 
can be shown that even the increase of the sand-banks 
may be greatly misunderstood and exaggerated. 

In its natiual state, the channel of such an estuary as 
the Lune or Oxe Kibble, as .already explained, is subject 
to constant change of position. I have seen many acres 
of marsh or grass land in such estuaries carried off by the 
sea, and the solid matter of which they were composed 
scattered over the shores and sand-banks. Now, the 
effect of fixing the channel by means of walls, in the 
manner recommended, is to form one permanent navigable 
track ; and the banks on either side, being no longer sub- 
ject to the periodical inroads of the river or tides, gradu- 



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306 INLAND NAVIGATION. 

aUj- rise in elevation until the^ axe capable of producmig 
vegetation, and ultimately become what are termed marab 
lands. When a river channel has been thus fixed and 
confined by walls, I have ascertained by repeated obser- 
vation that the tidal water comes up the channel in a 
comparatlToly pure state, instead of being loaded -wiih 
particles abraded fi*om the sand-banks and marshes. It 
baa also been found that the process of deposit at the 
sides of an estuary bo improved goes on very slowly after 
it has reached a certain stage ; for the materials deposited 
on the upper parts of the banks are, as after\rarda more 
particularly described, exceedingly fine, and are carried 
only by the highest tides, which seldom reach those 
elevated portions of the shores. From all these con- 
siderations I infer that the effect of river-walls upon an 
estuary is mainly to prevent the constant disturbance of 
the materials of which the banks are composed, but not 
necessarily to occasion additional accumulations. 
AsteataiiiatiM I had an opportunity, at the Lune, of testing by 
actual measurement in how &r the raising of the banks, 
caused by the erection of the walls, was due merely to a 
new disposition of the materials which originally filled the 
bed of the estuary, or to additional foreign mattera 
deposited in consequence of the operationa. I am not 
aware that similar observations with ibis object have 
been made on so large a scale ; and as tbey are highly 
important in assisting our views as to the economy of 
tidal estuaries, I shall give a brief notice of them. 
iDereaw or tidal On referring to the chart of the Lune, Plate YIII., 
i^nns and T*r- ^^^ changing nature of the channd will be seen from the 



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KBOLAHATIOK AND FROTBCTION OF LAND. 307 

di£krfflit courses in which it flowed, as shown by dotted 
lines. To obviate this, training walls and other works 
were constructed, which caused, as might have berai ex- 
pected, a veiy considerahle alteration in the position and 
form of the sand-banks in the estuary. This alteration, 
in connexion with the depression of &om two to three 
feet in the low-water level of the river, was apt to lead a 
casual observer to suppose that a great accumulation of 
sand had taken place, and consequently that a correspond- 
ing amount of backwater had been excluded, and obser- 
vations were made to determine the state of the case. 
Fig. 61 represents the changes that were produced by the 
works. Over the whole area, which is represented as 
covered by sand, a deposit had taken place, the banks 
being higher than formerly, whereas the whole area in- 
cluded in hatched lines had been scoured, the banka 
having been lowered. A caxe^ calculation was made, 
founded on numerous sections taken in 1838 before the 
works were commenced, and in 1851 after their comple- 
tion. The result of this investigation was, that after the 
completion of the works the amoimt of deposit on the space 
shown as sand in the cut was 3,070,146 cubic yards; 
while the amoimt of scour on the space shown by hatched 
lines was 2,810,449 cubic yards ; giving an excess of de- 
posit of 259,697 cubic yards. But the amount stated as 
having been scoured does not include what has been taken 
away below Glasson and Basil points ; which has doubt- 
less been deposited in the bank above. The survey of 
1838 did not afford data for ascertaining the amount 
of what had been scoured below Glasson with sufficient 



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INLAND NAVIGATION. 




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RECLAMATION AND nuyFECnON OF LAND. 309 

accuracy to admit of its being included in the foregoing 
calculationa But an amount of scouring was aBcertained 
to have actually occurred at that place, which was amply 
sufficient to counterbalance the surplus of 259,697 cubic 
yards of d^>0Bit, as given in ihe above statement. 

Such a result may indeed be expected ; for it is diffi- 
cult to conceive in what way parallel walls formed in an 
estuary can operate either in bringing down additional 
alluvial matters from the river above, or in bringing up 
additional detri.tus from without the bar. 

Holding these views, and supported by the actual 
obserro-tions made in the case of the Lune, I, therefore, 
conclude tliat the tendency of works executed in accord- 
ance with the principles laid down is not necessarily to 
produce additional accumulation of matter, but simply to 
alter the disposition of the existing materiah ofv^ich the 
bed of the estuary was originally composed. 

But assuming that in some cases a deposit does take 
place, and that the gradual rising and ultimate reclama- 
tion of marsh land excludes a certfdn portion of tidal 
water, it is important to consider in bow fer such 
abstraction of water is counterbalanced by the navigar 
tion works, and on a full consideration of the matter 
it will be found tliat the compensation afforded by well- 
designed works is veiy much greater than is generally 
supposed. 

I have already said, at page 226, in considering the 
question of scouring power, that the aggregate annual 
e&ct of the additional water gained by the operations 
on the Tay was equal to two months' flow of the river 



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310 INLAiro NAVIGATION. 

in Its ordinary state. I liave also shown, at page 283, 
that the water so gained acta on the low-water chaonel, 
and is th^^ore calculated to produce what may be called 
the maximum scouring power. As we are now speaking 
of land reclamation, it may be well stall farther to con- 
sider what relation this additional scouring water bears 
to the sheets of shallow water which are' ^read over 
exten^ve areas when covered by high tides. Perhaps I 
shall beat give an idea of this by stating one or two 
examples from actual practice. 

As regajxis the Tay, we have seen that the addUional 
quantity of water filled and emptied every tide is one 
million cuhic yards, and this occurs 730 times in the year. 
Now, it is interesting to ascertain in such a case what 
area of land could be enclosed without impairing the 
beneficial efiect of the tidal scour. Aaannning that the 
roarsh lands proposed to be enclosed may have been 
covered five or six times during each set of spring-tides, 
or say 144 times during the year, to the average depth 
of 1 foot, the eflEect produced upon the navigation, by the 
ac^ired and abstracted tidal water, may be expressed in 
the following manner : — 

Foxmding on the formula, S oc V T, already given at 
p. 283, 

Coble Tuda. 

Let VT = the acquired water, viz., 1,000,000 x 730 = 730,000,000 
and vt the abstracted water per ) 43,600 x 1 „ , . . _,_ _-_ 

acre of reclaimed land, ) 27 

ti,«. ^ 730,000,000 ,,,, 

*'""-;r- 232:272-=""'''=^ 

— ^thua showing, that the improvements effected on the 



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RECLAMATION AND PBOTECnON OF LAin). 311 

river were such as to allow of the reclamation of 3143 
acr^ of land at the level referred to, without diminiafa- 
ing ihe original scouring effect of the tidal water. In 
other words, on the Tay, there might be encloeed an area 
of marah land covered to the average depth of 1 foot 
during spting-tides, equal in extent to the whole sur^ 
£ice of the river from Perth down to about 2 milea 
bdow Newburgb, before excluding an amount of water 
equal to the aggre^te quantity brought in by the navi- 
gation works. 

On tiie Bibble, also, additional tidal water, unount- 
ing to 1,745,000 cubic yards, has been gained by the 
lowering of the river, and, applying the same calculations, 
this represraita an extent of marsh land of 5484 acres, 
being equal to the whole area of the estuary from Preston 
to about a quarter of a mile below the Naze Point. It will 
thus be seen that, even if we assume the land to be covered 
to a greater average depth than 1 foot, there is ample 
room £)r reclamation, within certain limits, on properly 
treated tided estuaries, with advantage both to the interests 
of the navigation company and the proprietors of land. 

It is obviously highly important if the two objects 

i> • 111- 1 ■ 1 • 1 P^''? benefited 

of r%ver and Umd miprovement can be earned on sunul- by tma 
taneously ; and to a lai^ extent this, as has been shown, ^^^'^ 
is pOTfectly practicable. The attempts of proprietors to 
protect the foreehores of their lands frum the encroach- 
ments of rivers in tidal estuaries, are often attended with 
great expense ; and if those efforts prove for some time 
effectual in warding off the approach of the channel, 
the land speedily takes on v^;etation, and is fit for 



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312 INLA.ND NAVIOATION. 

pasture. But the tenure by which such property is held 
is very slight ; and the spot which to-day affords grazing 
for cattle may in a few tides become the navigable chfuinel 
- of the river. Now it is ohvioiis that the perfect protec- 
tion fi:om such encroachments afforded by the training 
and guiding of the low channel by longitudinal walls, 
adds materially to the value of the adjoining property ; 
for not only is the land beyond high-water mark com- 
pletely protected from encroachment, but the marsh lands 
bordering the estuary become, in &ct, permanent property, 
and not an ever-chaDging benefit, held for one year and 
probably lost the next. Marsh lands so protected froim 
waste are still, it is true, liable to be flooded by high 
tides ; a circumstance, however, which is considered by 
some persons not injurious, but rather benefidal for marsh 
pastura 

The process of land reclamation to which I have 
alluded is generally termed "warping." In most cases 
the tide is permitted to flow &eely over the sur&ce, and 
whatever is deposited at slack tide contributes to t/he 
accretion. Sometimes the laud-making is hastened l^ 
forming banks with sluices, and retaining the water till 
it deposits the whole of the matter in suspension, and 
then p^mitting it to run off slowly. 

It is obvious that the rate at which the process goes on 
depends on the quantity of matter held in suspension, which 
varies in different estuaries. The size of detrital particles 
whic^ are carried by the currents of estuaries depends 
on the vdocity of the stream, the nature of the bottom 
along which the detritus is moved, as well as the shape 



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RECLAMATION AND PROTBCTION OF LAND. 3l3 

of the particles of which the detaitus itself is composed, 

and is altogether a subject so dependent on special cir- 

cumstanceSj that it is impossible to lay down rules which 

can be generally applicable. I must therefore content 

myself with giving results as communicated by different 

authorities, !Before doing so, however, I may state a rule 

which I have found to apply to the Dee, Kibble, Lune, 

and Wear, and which I believe to be generally applicable. 

It is, that in all tidal estuaiietf the heavier sands ^''"^Ba.vint 

deposits are found on the banks at the movik of iAe°'»tt«'in«d»i 

^ •> ^ Mturica found 

estua/ry, and the particles are lighter as we recede inwards. "«* "" ■«»■ 
I have tested this on the rivers above mentioned, and 
others, by a^tating equal quantities of sand and deposit 
(taken from different parts of the tidal estuary) in equal 
quantities of water, and observing the time which elapsed, 
in each case, before the materials were deposited and the 
water assiuned a state of purity. 

The result of these obeeivBtions proved that the sand 
of outer or seaward banks, where the currents were strong, 
was composed of large particles, held in suspension only 
a few seconds, while in the inner parts of the estuary 
the deposit decreased in weight, and generally that it 
decreased from low to high water where the currents were 
weak and where the silt was exceedingly fine, and re- 
mained in suspension, in some cases, even for hours after 
the a^tation of the water. 

It win be seen that the rule I have stated is at vari- 
ance with that propounded by Frisi, and also by Sir H. 
de la Beche,^ in the following terms : — " Where the velo- 

' Da la Beche's Oeologieal MannaL 



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314 HfLAND NATIOATION. 

city of a river is sufficieiit to produce attrition of the 
subetances which it has either torn up, collected by 
undenmning its banks, or which have &llen into it, they 
gradually become more easy of transport, and woxJd, if 
the force of the current continued always the same, be 
forced forward until the river delivered itself into the sea; 
but as the velocity of a current greatly depends on the 
fall of the river, the transport is regulated by the inclina- 
tion of the river's bed. Kow it is well known l^t this 
inclination varies materially even in the same river, so 
that it may be able to carry detritus to one situation, but 
may be unable to transport it further, under ordinary cir- 
cumstances, in consequence of diminished velocity. As 
a general &ct, it may be &irly stated that rivers, where 
their courses are short and rapid, bear down pebbles 
to the seas near them, as in the case of the Maritime 
Alps, etc. ; but that where their courses are long, and 
change &om rapid to slow, they deposit t^e pebbles 
where the force of the stream diminishes, and finally 
transport mere sand or mud to their mouths, as is the 
case with the Rhone, Po, Danube, Ganges, etc" This 
holds true in the case of such rivera as those to which 
Sir H. de la Beche refers; but it will be foimd, as 
I have stated, that the case is exactly reversed in tidal 



Sin at partidea The following are the results of experiments made 
ue etfuu of by Bossut, Du Buat, and others, on the size of detritsl 
""'"'*' particles which streams flowing with differait velodties 
are said to be capable of carrying : — 



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KECLAMATION AND PROTECTION OF LAND. 



315 



3 in. per sec = 0-170 mile per hour vill, just be^ to work on 

fine claj. 
G „ „ = 0'3i0 do., will lift fine Band. 
8 „ „ = 0'i6i5 do., will lift sand as conrse as linseed. 
12 „ „ = 06819 do., will sweep along fine gravd. 
24 „ » = r3638 do., will roll along rounded pebbles I incb 
in diameter. 
3 ft. „ = 2*049 do., wiU sweep along slippeiy angular stones 
of the size of an egg. 

The following experiments were made by Mr. T. 
Login, C.K, and are given in the Proceedings of the 
Royal Society of Edinburgh, voL iii. p. 475. They were 
made with a stream seldom exceeding half ao inch in 
depth ; and are as follows : — 



Brick-olay when mixed with water, \ 
and allowed to settle for half-an- v 
hoar, I 

Fresh-water sand, .... 

Sea-sand, 

Bounded pebbles about the size of t 
pew. J 

Vegetable soil, .... 



-666 



rent per 



40 
66-22 



■170 



■454 
■752 



Brick-day in its natural state was not moved by a corrent of 1 28 
feet per minnte, or Vib mile per hour. 

The following statement by Mr. William Bald, ofwaightorde. 
experiments made on materials taken fit)m different parts b«i of th« 
of the bed of the Clyde, shows the variety of materials 
found in the same stream, and is a valuable record of 
ihe weight of the deposits which form the beds (^ om- 
tidal rivers :' — 

> MintOM nt Proeerdingt (jf IiutUtUion nf Chil Ettginttn, vol. r. p. 330. 



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INLAND NATIOATION. 



Quuitit; of 
matten hald in 
■tupBoiloa by 
dlffennt riTen. 



D.pa.11.. 


LlstocnUc 


No. ofenWo 
feat to tha ton. 


Fine aand and a few pebbles laid in tJie box I 
loose, not pressed, nearly diy, . . J 

Do. do. pressed 

Mod at White Inch, dry, and firmly packed; > 

Wet mud, lather compact and firm, weU 1 
pressed into the box, . . . / 
Wet, fine sharp gravel, well pressed. 

Wet mnning mud, 

Sharp dry sand deposit in harbour, 
Pt.-Gh»sgow Bank, (sand) wet, pressed into a box. 
Sand opposite ErsMne House, wet, pressed, . 

Alluvial earth, pressed, 

„ „ loose, 


87 

93 
97 

lie 

124 
122f 

92 
1204 
116 

93 

67 


26 
U 
23 

19 

18 

18-1 

34-3 

18-6 

19-3 

24 

33 



I found the gravel of the Tay to be 18 feet to the ton. 

The quantity of Bolid matter carried or held iu sus- 
pension by riveiB, has also been made the subject of obser- 
vation. Different observer whose remarks have come 
under my notice, have stated their results in different 
ways, some giving the weight and others the bulk of 
detritus. Thus Mr. Ellet says that the sedimentary 
matter transported l^ the Mississippi forma -^^^th part 
of the volume discharged by the river.^ Mr. T. I/^in, 
C.E., Pegu, states, in a paper on the Delta of the 
Iirawaddy, read before the Royal Society of Edinburgh, 
session 1857, that the waters of the Irrawaddy contained 
-jn'jnjth part of their iveight of sediment during floods, 
and TTVyth part of their weight when the river was in 
a low state, and ^ves the mean depoat at 8 inches per 
cubic yard. Mr. Leonard Homer found that the water 
of the Bhine at Bonn contained fixim xriinF^ P^ ^ ^^ 

> Ellet, On the Ohio and Mintst^i. 



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BECLAMATION AND PROTECTION OF LAND. 317 

weight during floods to ^irfyrtt part of its weight in 
a low state.^ Captain Denham found that ihe tidal 
water of the Mersey contaiued 29 cubic inches of solid 
matter in every cubic yard during flood-tide, and 33 
cubic inches in every cubic yard during ebb-tide.' Sir 
Charles Lyell says: — "Hartsaeker computed the Khiue to 
contain, when mtmt flooded, 1 part in 100 of mud in sus- 
penaon. By several observations of Sir George Staun-' 
ton, it appeared that the water of the Tellow River in 
China contained earthy matter in the proportion of 1 
to 200. Manfredi, the celebrated Italian hydrographer, 
conceived the average proportion of sediment in all 
running water to be rfstl^* Some writers, on the con- 
trary, aa De Maillet, have declared the most turbid 
waters to contain flir less sediment than any of the 
above estimates would import ; and there is so much 
contradiction and inconsistency in the &cts and specula- 
tions hitherto promulgated on the subject, that we must 
wait for additional experiments before we can form any 
opinion on the subject." ' 

But assuming 18 cubic feet of solid matter to weigh a 
ton, the following table presents a feir view of the cubic 
measure of solid matter, and the ratios of volume and 
wfflght in each case. In submitting this table, I must 
observe that the discrepancies in the statements are so 
great, that further observations are necessary before any 
satiflfiictory conclusion can be arrived at ; but I give tiie 

* Arcana qfSdtnct and Art, 1835. 

* ObioTatbHu on the Mtrtey, by C»i)t»m H. M. Denlifmi, S.X., LiYerpool, 1640. 
■ PrmeipU* iff Otology, by Chmrles Lyell, F.E.S., LoDdoii, 1830, voL i. p. 247. 



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INLAITD NAVIGATIOir. 



results as th^ have been stated by tbeir respective 
authoritJTO : — 



HuwotBlTa. 


Cubic IncbM nf 
Klldm.tt«lD 


lUtiMorTolBma 

ofioUdmitter 
toyolnmof 






lS-5 


^<r 


lAi 


Ir»w»ddy, in flood, . 


11-71 


rhx 


Wi,. 


Do., otdiui; atkte. 


41 


nirt 


.Ai 


RUne, in flood, . . 


1-87 


fiItf 


Tiinw 


Do., ordiuMj tUte, 


I-IS 


illBH 


nIzT 


Do., me«n, . 


IB 


Bliol 


TTTn 


MerBey, flood.tid», . . 


29- 


nW 




Do., ebb■^<l^ 


33- 


tA. 



From this table it appears tbat the Kbine, as com- 
pared to the others, is exceedingly pure ; while tte 
waters of the Mersey, on the other hand, hold ia suspen- 
sion a very large amount. It must be kept in view, how- 
ever, that the source whence the sedimentary matter in 
the Mersey is derived, is yery different from any of the 
other cases mentioned in the table. The main part of 
the solid matter in suspension in the Mersey, and indeed 
in all our tidal rivers, is sand, stirred up by the flowing 
tide, and deposited again during the ebb-tide. The sedi- 
mentary matters in such rivers as the Mississippi or the 
Irrawaddy, on the other hand, are borne down &om the 
low tracts of alluvial coimtry through which it flows, and 
form a constant and consequently increasing deposit at 
the lower parts of the river. 

In all cases where the tidal currents across the mouths 
of such rivers are languid or alt(^ther absent, as in Ote 



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RECLAMATION AND PROTECTION 07 LAND. 319 

Missisdppi, the Nile, the Danuhe, oad other contmental 
rivers, the dep<»it8 brought down are not carried awaj, 
but form deltas, which collect with greater or less rapi- 
dity in proportion to the quantity of material brought 
down and the depth of water in which it is dep(»ited. 
Mr. Ellet computes the delta of the MisGossippi at 40,000 
square miles in extent, its average length from, north to 
south being 500 nules. Assuming the sedimentary matter 
brought down at -^^j'ljQth of the volume of water, and the 
dischai^ of Hhe river at 21,000,000,000,000 cubic feet 
per annum, he estimates that this vast accretion of de- 
posited stnflr must have formed at an average rate of 1 
mile in 99 years, giving a period for its entire formation 
of something like 45,000 years t Sir H. de la Beche has, 
however, with reason suggested that deltas would in- 
crease most rapidly at the first period of their formation, 
on account of the greater declivity of the river, and the 
supposition tiiat the detritus from the interior would 
become gradually less, from the equalization of levels and 
the fewer asperities that agents have to act on ; and thus 
it seems impossible to calculate frvm ihe present rate of 
accretion the time whldi the whole mass has taken to 
accumulate. 

The depth of deposit annually left on the shores of 
estuaries varies as much as the amount held in suspension 
by the wateni. M. Bouniceau' states that marshes on 
the Seine require twelve years to rise to the level of high 
water, and gives thirty years for a similar action to take 
place on the Bay of Vays, and eighty years on the 

' Canttrveliom d la Mer, par M. BonniaeBo, ji. 185. 



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320 INLAJlID NATiaATION. 

Scheldt. Similar variations are to be found in state- 
ments made by vaiiouB authors. 

The moat rapid deposit which has come under my 
notica was near the mouth of the Avon, at the Severn, 
where the channel between Dumball Island and the shore 
was silted up to the extent of 32 feet in 7 years. Fig. 62 
represents a section of a stream where the summer water 
channel was deepened and confined by longitudinal walings. 
for sanitary purposea The river when in flood raised the 
banks on eiih^ side about 3 feet in seventeen years, the 
stuff being deposited in r^jular layers of sand and silt. 
But after the banks attained the height represented in the 
cut, the floods began to act on the sides of the channel, 
and the stream is now wasting away the accumulations 



A. 




that have been gradually made, and this wasting action 
will no doubt go on until the sectional area is large enough 
to allow the floods to pass off without a velocity sufBcient 
to carry away the banks. The dotted line represents 
the original channel, the hard line the deposited banks, 
and the hatched portion what has been wasted away. 
This tendency to enlargement close to the edge of the 
stream corresponds to what is represented as having 
taken place at the Lune, at p. 308, where it will be ob- 
served a narrow strip of scouring is shown on either bank. 
The interral opposite to the words "sand deposited," 



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I 



BBCIAUATION AND PBOTECTION OF LAND. 321 

where th^^ is no hatcbing, is hard ground, and no sand 
ever lay on it. 

The cost of reclaiming land covered to a considerahLe 
depth by the tide is very great. The estimate for enclos- 
ing 10 acres of land for an extensive and important public 
work on the shore of an estuary where the rise of tide was 
10 or 12 feet was £3000 per acre, and on the same estimate, 
but in a situation not so exposed, the cost of enclos- 
ing 30 acres for dock purposes was £2000 per acre. It is, 
however, to the reclamation by means of low banks of 
sheltered marshes on a high level that my observations 
must refor ; and so much depends on the situation as well 
as on the area enclosed by a given length of bank, that no 
idea of the cost of such works can be given that can prove 
generally appHcable. It is, indeed, for the same reason 
that I have avoided throughout the whole of this treatise 
giving tiie cost of the works I have described, as a certain 
expenditure in one situation might effect either &r more 
or &r less work if laid out in a different locality, and in 
no department of engineering does this hold more true 
than in river and marine works. 

The process of reclamation in all cases goes on very Level ot n 
slowly after it has reached a certain stage, because asundi. 
the banks rise they are more seldom covered by the 
tide, and the materials deposited on the inner and higher 
parts of the banks are, as already stated, exceedingly fine, 
and are carried only by the highest tides, which seldom 
reach them. Mr. Park has found on the Kibble the first 
indications of vegetation to appear about the level of 
high water of neap-tides, and this corresponds with my 



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322 INLAOT) NAVIGATION. 

own ol«ervatioii8 at other places. Mr, Grordon' also 
found that in the Norfolk estuary "the samphire began to 
settle on the sands which the neap-tides jxist cover," and 
that " grass began to grow about one foot above the 
samphire level," so that, the level stated may safely be 
taken as that at which vegetation commences on the 
estuaries of this country. The sur&ce will gradually rise 
1^ succeeding depc^its, till at last it reaches nearly the 
limit of high-water spring-tides, which I have found to be 
the height of different marsh lands. Mr. Mitchell has 
found the same result in the United States, as on com- 
paring the height of different marsh lands th^ level 
corresponded to that of " the ordinary high-water level"' 
Fig. 63 is a section iliustaiating the manner in -which 
such marsh lands are formed. The upper portion nearly 
at the level of high water is what is called " marsh," or 
" outmarsh," and is fit for grazing. In some places it is 
covered with reeds. Below this level to half tide the 
Bur&ce is covered with occasional patches of samphire ; 
&rther down there is what is called " slob," consisting of 
sand covered with mud ; and lower down there is sand, 
more or less pure according to the situation. 
waAir(nt>">- Such marsh lands as those I have described, if left 
Und*. unprotected, must remain for ever liable to be covered 

during high floods or tides, and therefore cannot be said 
to be available as arable land without the erection of 
considerable works for the purpose of protecting them 
&om floods and providing for their effectual drainage. 

> Beport on Norfolk Eatoaiy, b j L. D. E Gordon, C.E., OlMgow, 1BS6. 
* On tlte B«el«mAtiou of Tid« Lud^ 1869. 



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BECLAMATIOK AND PROTBCTION OF LAND. 323 




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324 INLAND NAVIQATIOIT. 

The erection of all such works ahould be well considered. 
There are aituations in which the construction of embaiik- 
ments for protecting land may be injurious to the in- 
tereets of navigation; there are others in which such 
works, if judiciously laid out, may be harmless ; but their 
effect in any case can only he determined by a careful 
consideration of the special circumstances of the locality 
in which they are erected, I know many cases where 
the intra«sts of navigation have been Bacri£ced by unwar- 
rantable encroachment ; and, on the other hand, instaaces 
are not wanting where even important works have been 
embairassed and crippled by an over-cautious regard to 
the principle of non~encroachment on the high-water line. 
With reference more particularly to the operations of 
landowners, it is notorious that in many cases attempts to 
reclaim or protect property have led to serious and costly 
legal proceedings between kmdowners and the local con- 
servators of navigations ; and this has in some instances 
arisen &om a feeling, on the part of the landowners, that 
their operations could not be regarded as prejudiciaL 
The local conservators, on the other hand, have generally 
no means of knowing what the ultimate intentions of the 
landowners are until their operations have proceeded so 
&r as to render it impossible, if the interests of navigation 
require it, to stop or to remove the works without con- 
siderable loss. A difference of opinion has thus been 
raised, which has too often ended in an ezpen^ve lawsuit. 
I have long held the opinion that it would in many, if not 
in aU, of oxir estuaries, be most desirable to have a line of 
conservation marked out by the Xj^slature for the regular 



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RECLAMATION AND PBOTECTION OP LAND. 325 

tion of all works for the protection of land, just as we 
now have lines defining the boundaries of sea and river 
fishings. Were such a line of conservation defined, the 
landowners could then with confidence, and without risk 
of challenge, enter on such works within the l^alized 
boundary as they considered necessary for the protection 
of their property, and a source of much difierence of 
opinion and expensive litigation would at once be re- 
moved. Of the cost of enclosing and maintaining such 
reclaimed lands, and their success as speculations, I am 
not enabled from any experiaice of my own to judge. 
But, referring to what has already been said at page 321, 
I can safely say that unless the sur&ce of the maish to 
be enclosed is on a high level, it is not expedient to enter 
on works for its reclamation. 

Even after enclosure the embankments have to be at- 
tended to, kept in repair at a constantly recurring expen- 
diture, and often additional works have to be empbyed for 
further protection ; and I have still shortly to notice some 
of the protection structures that have been erected in de- 
fending the banks of rivers and shores of estuaries. 

In Holland, as is well known, the reclamation and 
protection of land, both fitim the sea and &om rivers, has 
been carried to a greater extent than in any other 
country, and much usefiol information will be found on 
that subject, and indeed on reclamation generally, in the 
papers by Mr. Paton, Mr. Oldham, and Mr. J. H. MuUer, 
in the Proceedings of the Institution of Civil Engineers.^ 

There can be no doubt that a smooth surfiice tends 



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INLAND NAVIGATION. 



to preserve the banks of a river, The water having no 
obetruction glides gently past without disturbance. But 
if the river'fl banks have, from neglect, got into a rugged, 
unevai state, I have found that a very sluggish stream 
may produce an abrading action in excess of what its 
velocity seemed to warrant. The rugged outline of the 
bank produces on a small scale the effect described at 
page 176 as resulting from jetties. The projecting points of 
grass-covered alluvial sod act as so many obstructions to the 



current, and in such a case the abrading action of the river 
cannot be measured by the general velocity of the stream, 
but by the local velocity (if I may use the expression) with 
which it sweeps round, and gradually undermines the 
rugged parts of the bank. Although the passage of a float 
down the centre of a stream indicated a velocity too slow 
to abrade a river's bank, it would be erroneous to assume 
that therefore there are no local currents roimd the salient 
points of the foreshore strong enough to wear them away. 



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RECLAMATION AND PBOTECTION OF LAND. 327 

Sometimes stones are deposited to cover gently sloping 
banks, and where they are steep I have found piling and 
brushwood, arranged as shown in fig. 64, a veiy effectual 
protection for rivers having winding courses and soft beds. 

In other cases, in more open estuaries exposed to the woas for pn>- 

. tectliuioflaiid 

sea, works of a stronger kind are required. Figs. 65 and in op«n 

... > 1 • 1 J ert™*!!"- 

66 are a plan and section of a protection which was used 



on a line of shore composed of shingle. Jetties projecting 
from the shore had at first been used to collect the shingle, 



but I found that in heavy seas the waves were led along 
the jetties, and had a hurtful effect at their roots where 
they joined the beach. A continuous line of piling and 
planking was accordingly adopted, combined with oocar 
sional jetties, as shown above, and this has proved very 
successM In proof of this, it baa been found that 
wherever the upright piling and planking has been 



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328 INIAND NATIQATION. 

formed, there was no influx of anjUuDg beyond spray 
upon the adjoining land, but that at all other parts of the 
coast (which is about 6 miles in length), where the &ce 
of the beach is sloping, the water passed &eelj over in 
considerable depth, carrying drift timber &r into the fields, 
and in some places heavy shingle to the depth of 2 feet. 
The problem to be solved -vraa to oppose an obstacle which 
should throw back the sea ; and the upright &ce, &oxd. 
which the heavy portion of the sea recoils, is found to do 
this better than the sloping &ice. In order to encourage 
the collection of shingle, a second line of longitudinal 
piling was, at some places, formed in &ont, and parallel to 
the main line of defence ; and the works described have 
been fotmd a veiy effective defence on a line of shingle 
beach, exposed to a considerable sea, on the shores of the 
Bristol Channel 

In designing all sudi works, however, the engineer 
must be guided by the formation and exposure of the 
shores, the kind of materials most easily available, and, 
above all, the value of the property endangered, as every 
engineer must know by experience that in some situations 
protection can only be secured at a cost out of all propor- 
tion to the benefit which it would confer. 



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CHAPTER XIV. 

CBOssma op navioationb by railway bbtoqes. 

The interests of railway companies uid the conser- 
vators of navigations are often antagomstic. It is not 
unfrequently an object of great importance for a railway 
company to obtain a crossing over a navigable river, and 
they not unnaturally, in their zeal to promote the in- 
terests of their shareholders, tmdervalue the importanoe 
of navigation. The consequence ' is, that many of iiie 
hardest Parliamentary battles have of late years origi- 
nated in the conservators of navigable rivers resisting the 
attempts of railway companies to carry out their schemes 
with little regard to the obstruction they may interpose 
to sea-borne traffic, or the ruin they may entail on old- 
established trade. 

The question as to the propriety of permitting a rail- 
way to cross a navigation, must obviously depend on the 
relative importance of the railway and river traffic — the 
amoimt of interference proposed — ^ttie interests of those 
connected with the two trades, and many other points 
which it is neither my province nor intention to discuss 
in this place. But so much has the question of bridging 
navigable rivers of late been brought under notice, that it 
seems desirable to lay before the reader a statement of 



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330 INLAND NAVIGATION. 

the general grotinds on whic^ such mterfereuces have 
been opposed on behalf of the mteresta of navigation, as 
being a not unsuitable topic in connexion with the subject 
of river improvements which we have been considering. 

It ia not my intention to refer to Bchemes for croaaing 
rivers by high-level bridges of great span, but to the more 
general interfer^ice caiised by railways crossing on a low 
level, with opening spans for the passage of vessela 

It is both natural Euid neceasaiy that the conservators 
of the public highways, afforded by rivers, should look 
with no friendly eye on any attempt to obstruct or 
injure their usefrdness. The public owe much to the 
firm, and in many cases succeesful, opposition offered 
on their behalf to some schemes of railway companies 
designed to cross a navigable river, in order to save a 
few miles' detour or avoid using part of the line belonging 
to another company, I do not by any means say that 
all railway crossings are, or have been, of this diaracter. 
There are, and may again be, cases where the benefit 
derived 1^ the public from a railway bridge across a 
river, so greatly outweighs any benefit that can possibly 
be derived from preventing its erection, that the naviga- 
tion may freely yield to tfie railway. But this is not 
always the case; sometimes the two interests may be 
fiurly balanced, and in other cases the proposal to bridge 
a navigable river cannot for a moment be entertained. 
No one at present would dream of interposing a railway 
crossing and swing-bridge betwlsen London and Green- 
wich, or between Gla^;ow and Greenock. 

The objections to such crosednga have generally been 



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CRossma of navigations by bailway bbiboes. 331 

argued &om two distinct points of view, the one founded 
on nauticcU, and the other on engineering grounds. 

The nautical question refers to the mode of navigating 
our tidaJ rivers, and the difficulty of taking vessels 
through the narrow opening of a swing-bridge in a rapid 
tide-way. The arguments adduced are, that our rivers 
are entirely dependent on the flow of the tides, and are 
navigable for ships, only when the tidal water is in the 
channel. At low water they are shallow fi^sh-water 
streams, sometimes navigable only by small boats. The 
time for the passage of lai^ vessels is restricted to one or 
two hours before and after high water, and it is absolutely 
necessary for vessels to take advantage, not only of high 
water, but of the best tides, both in making and leaving 
the ports on rivers. Every obstruction, therefore, that 
may tend to hinder the progress of a vessel, and lead to 
her losing a tide, is a very serious evil, and renders it 
desirable that no obstacle should be placed in her course. 
Unless vessels can run freely in and out, they will not 
continue to frequent a port. 

For the same reasons objections have been raised to 
the control which such a crossing places in the hands of 
the company. The opening of the loidge must be so 
reg^ulated as to smt the passes of trains, which is, or 
ought to be, regular, whereas the time of high water 
varies from day to day. These, and other objectionB, 
have been often advanced to show the incompatibihty of 
the two interests. 

The engineering objections are foimded mainly on 
the &ct that piers placed in the water-way of a river 



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333 mLAND NAVIGATION. 

disturb the currents and cause shoals, as will be best 
understood by referring to page 190, where the effects of 
such disturbances are &II7 discussed. If the bed of the 
river is composed of rock or other hard material, ihe 
objection founded on shoaling ceases ; but in a river 
having a bed of gravel, or, still worse, of sand, the case 
is very different. The amount of scour will vary with 
the state of the tides and the amount oi fresh in the 
river, and shoals must necessarily be thrown up, varying 
in position and amount according to the currents which 
produced them. These obstructions, as we have seen, 
may be caused by a single tide, so that no apphcation of 
dredging can remove \h.& objection in sufficient time to 
restore the navigable depth of channel for passing vessels. 
It is well known that the shoalest water becomes the 
ruling depth of the navigation, and a shoaX which reduces 
the depth by one foot, only at one point, practically 
reduces the depth for navigation by that amount. So 
that if, after high spring-tides or a heavy flood in the 
river, a shoal is caused above or below the bridge, it 
becomes a formidable impediment, all the more so that 
the railway company, with the very best intention, can do 
nothing to remedy the evil, which may spring up in a 
single night. This introduction of any element of un- 
certainty as to depth is perhaps the greatest evil that 
can be inflicted on the interests of a port. 

An artificial covering for the bed and banks of the 
river, similar to what has been described in C3hapter VIIL, 
may perhaps be suggested as a remedy. But such a 
covering would require to extend for a great way on 



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CE08SINO OF NAVIQATIONB BY BAILWAY BRIDGES. 333 

either side of the bridge, and woxild be enormously costly, 
whatever the material employed. It would prevent fur- 
ther deepening of the river, and no vessel could drop 
anchor on it. Above all, it might be found that the 
sudden change team a hard to a soft bed at either ex- 
tremity produced disturbance of ciurents and shoals as 
inconvenient as those caused by the piers of the bridge 
which it was designed to prevent. 

Swing-bridges have been sanctioned on several navi- 
gable rivers, and attempts' to erect 'Uiem on others have 
been successfully resisted. The railway authorities have 
invariably admitted that if such crossings are allowed, 
they should be arranged so as to be as little injurious bb 
possible ; and as I believe the hydraulic swing-bridge, 
designed for crosung the Ouse near Goole by Mr. T. K 
Harrison, is iiiB most perfect structure of the kind that 
has been made, I shall give a short description of its lead- 
ing features, referring the reader for details to the elaborate 
description and drawings communicated to the Institution 
of Mechanical Engineers, by Sir William Armstrong. 

It will be seen from Plate XVI., which is from Sir 
W. Armstrong's paper, that the bridge has seven spans. 
The main pier, which is about 40 feet in width and 250 
feet in length, is placed in the deepest part of the river. 
On this pier the moveable part of the bridge revolves, 
forming, when it is open, a passage for vessds of about 
100 feet in width on each side of the pier. 

The following are some of the general descriptions 
and dimensions, from the paper referred to ; — 

" The total length of the bridge, £zed and moveable. 



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334 INLAiro NAViaATION. 

is 830 feet. The fixed portions consist, of five spaziB, of 
116 &et each &om centre to centre of pier& Each of 
the piers for the fixed spans consists of three cast-iron 
cylinders of 7 feet diameter, and about 90 feet length. 
The -depth from the under side of the bridge to the bed 
of the chaimel in the deepest part is about 61 feet. The 
headway beneath the bridge is 14 feet 6 inches from 
high-water datum, and 30 feet 6 indtee firom low-wat«'. 
The swing portion of the bridge consista of three main 
wrought-iron giiders, 250 feet long, and 16 feet 6 inches 
deep at the centre, diminiabing to 4 feet deep at the 
ends. The centre ^rder is of larger sectional area than 
the side girders, and instead of being a single web, is 
a box g^OT 2 feet 6 inches in width. An annnlar box 
girder, 32 feet mean diameter, is situated below the centre 
of the bridge, and forms the cap of the centre pier. This 
girder is 3 feet 2 inches in depth, and 3 feet in width, 
and rests upon the top of six cast-iron columns, each 
7 feet diameter, which are arranged in a circle, and form 
the centre pier of the bridge. Each of these columns 
has a total length of 90 feet, being simk about 29 feet 
deep in the bed of the river. A centre column, 7 feet 
diameter, is securely braced to the six other columns by 
a set of cast-iron stays, which support the floor of the 
engine-room. This centre column contains the accumu- 
lator, and forms the centre pivot for the rotation of the 
bridge. 

" The weight of the swing bridge is 670 tons, and 
rests upon a circle of conical rollers. These are twenty- 
six in number, each 3 feet diameter, with 14 inches width 



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CROBSraO OP NAVIGATIONS BY RAILWAY BBIDQES. 335 

of tread, and made of cast-iron hooped with steel They 
run between the two circular roller-paths, 32 feet diameter, 
and 15 inches hroad, which are made of cast iron, &ced 
with steel ; the axles of the rollers are horizontal, and 
the two roUer-paths are turned to the same bevel 

" The turning motion is communicated to the bridge 
hj means of a circular cast-iron rack, 12i^ inches wide on 
the fece and 6^ inches pitch, which is shrouded to the 
pitch line, and is bolted to the outer circumference of the 
upper roller-path. The twik gears with a vertical bevel 
wheel, which is driven by a pinion connected by inter- 
mediate gearing with the hydraulic angina There are 
two of these engines, duplicates of one another, and 
either of them is sufScient for turning the bridge, the 
force required for this purpose being equal to about ten 
tons appHed at the radius of the rollers' patii. Each 
hydraulic en^aie is a three-cylinder osdllating engine, 
with simple rams of 4^ inches diameter and 18 inches 
stroke. These engines work at forty revolutions per 
minute, with a pressure of water 700 lbs, per inch, and 
are estimated at forty horse-power each. The steion- 
engines for supplying the water-pressure are also in dupH- 
Cate, and are double-cylinder engines, driving three throw 
pumps of 2f inches diameter and 5 inches stroke, which 
deUver into the accumulator. The steam cylinders are 8 
inchee diameter and 10 inches stroke, each engine being 
twelve horse-power. The accumulator has a ram 16| 
inches diameter, with a stroke of 17 feet It is loaded 
with a weight of 67 tons." 

There are other interesting details, showing the highly 



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336 INLAin) NAVIGATION, 

ingenious mechamsm designed by Mr. Harrison and Sir 
W. Armstrong, for adjusting the bridge so as to obtain a 
perfectly solid roadway, and for other arrangements con- 
nected with the railway trafific, into which I need not 
enter. Sir William closes his paper by stating that " the 
time required for opening or closing the bridge, including 
the locking of the ends, is only fifty seconds, the average 
speed of motion of the bridge-ends being 4 feet per second. 
For the purpose of insuring safety in the working of the 
railway line over the Inidge, a eystem of self-acting 
signals is arranged, moved by the fixing gear at the 
two ends of the bridge ; and a signal of ' all right' is 
shown by a single semaphore and lamp at each mid of the 
fixed parts of the bridge ; but this cannot be shown until 
each one of the locking bolts and resting blocks is secure 
in its proper place." 

It has sometimes been proposed to cross navigations 
by carrying the railway below the bed of the river ; and 
if this could be done by tunnelling, the objections to 
which allusion has been made would be entirely obviated. 
But the schemes brought before Parliament for under' 
water crossings have invariably been coupled by a pro- 
posal to execute the works by open cutting, either by 
diverting the river or constructing cofiferdfuns in ita bed. 
The diffictdty of dealing in this manner with a large river, 
without, for a considerable period, seriously obstructing 
its navigation, and the obvious disadvantages of such a 
crossing, both as ' regards gradients and drainage, have 
hitherto, so &r as I know, prevented any such scheme 
being passed by the L^;islatura 



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INDEX. 



ABKRSSKir SAKMxrtt, dirersiiw of river 

Dee at, 197. 
Amuon, bore on, 108. 
diitftnce at which ita WKtert are 

vioible at sea, 131. 

phyaical charaoterutica of, 337. 

Anuterdam Canal, 3a 

mode of dredging on, 209. 

AodertoD, Dr., 99, 110. 

Aonan, river, pbTiical bharaoteriitiei 

of, 337. 
Amutrong, Sir W., 333. 
Artifioial beda nnder bridge^ 180, 333. 

Backwatke; importanoe of, 277. 

different aspects under whiah it 

may require to be conaidered, 27S. 

general propoaitioiia regwding, 284. 

level of obctmotion o^ 282. 

•eeBara. 

Bag uid «poon dredging, 198. 

Bakker, M., 32. 

Bald, W., 218, 227, 31G. 

BaUjmhannon, hard bar at, 300. 

Banks, canal, protection of, at water- 
line, 18, 21. 

wasting of, by haulage and steam- 

towiog, 20. 

of riven, effects of staam-towiog 

on, 20. 

rugged, cause oarrenti, 326. 

w^s for protection of, 326. 

Barge canals, 1. 

Baiibolomew, W. H., 20. 

Barton, J., 217. 

Ban, 263. 

Danube, 297. 

deflnitioD of, 264. 

^^^— changee in ffhannfflii thnragb, 2i 

eause* of, 288. 

conditiona noder which sand-bars 

are formed, 271. 

depth of water over various, 265. 

due to Bconr, 274. 

average, uniformity of, 289. 



Ban^ eetoarial sand-ban not improreabl^ 

nnlesi at great cost, 28S. 

hard, 300. 

origin of, 267 ; Caatelli on, 269 ; 

EUet on. 293. 

pisn for protection of, 290. 

shalloweit after heavy seat, 273. 

Barless estuaries, 271. 

Basins, tide, 268. 

Batenaa, J. F., IS, 40. 

Beardmore, N., 100, 145, 337, 338. 

Beche, Sir E. de la, 313, 319. 

Beds of rivers, beneficial reenlls from 

redaction of the inclination of, 224. 
Beechey, Admital, 166, 170, 226, 338, 

339. 
Belfast quays, 260. 
Blanken, M., 32. 
Blasting previona to dredging, 212. 

under water by gnn-ootton, 215. 

Bore in rivers, oaoae of, 163. 

on the Amazon, 168. 

on the Dee, 164. 

on the Severn, 166. 

Borings, 94. 

Boaaut, 314. 

Boaniceam, M., 319. 

Boyne, physical chanateriattOB of, 337. 

Bridges, pien of, obstnict tidal flow, 

180. 

artiQcial beds nnder, 180, 332. 

railway, orosiing navigationa, 329. 

Bridgewater canals, 8. 

Brindly, J., 8, 9. 

Bristol Channel, works for protecting 

land at, 327. 
Brooks, W. A., 339. 
Bnduuian, O., 280. 
Bnoket-dredging, 199. 

Casboyse Canai, B. 

Caledonian Canal, 29. 

Calver, CB.ptKiii, 119, 254. 

Camel for floating vessels over shoals, 



Digiizedb, Google 



342 



Cuiml — AmnterdAin, 33 ; Bridgewster, 
8 ; Coerdyhe, 5 ; CaledoniftD. 29 ; 
Crinan, 28 ; Firth of Clyde, 27 ; Fosi- 
dyke, 6; Or««t Western, 16; Gloil- 
oeater, 21; Longuedoo, B, 27 i Uonk- 
land, 16 ; Morris, U ; North HolLuid, 
31 ; Saez, 39. 

Cuula, barge,. 1. 

buika of, protection ftt water-line, 

18, 21. 

watting of, by haulage and 

iteam -towing, 21, 24. 

Chinese, 5. 

hanlage on, 20. 

inclined planes and perpendicnlaj 

Urts, S, 14, 15. 

lock^ inTention of, 3. 

, double-acting, 35. 

sizee of, on barge canals, 13. 

off-let*. Cor emptying, 17. 

pitching of banks, IS, 21. 

pnddling for, 18. 

reaches and locks of, 13. 

Bhip, 27- 

iectional area of barge, 12. 

steam-towing on, and its effect on 

the bank* of, 20,21. 

stop-gates of, early, 5. 

16. 



Ifl. 

waste-wei™ of, 15. 

tvater, snpply of, 11. 

C&rlingford Loch, dredging id, 217. 

Carpenter, Dr., 119. 

Castelli's theory of bars, 269. 

Cay, W. D.. 197, 

Channels of some rivers liable to c 



through sand - banks over bus, 

changes in, 286. 

making walle for guiding, 183. 

permanent, obji>ct of river-works 

to secure, 186, 227. 

sabsidiary closing of, 193, 

Chapman, W., 253. 

Chesney, General, 41. 

Clarke, Colonel, 40, 47. 

Olegram, W. R, 20, 21, 22. 

Clyde, bed, nature and weight of mate- 
rials composing, 310, 31G. 

dredges, dimensions of, 20*. 

dredging, amount and cost of, 

202. 

excavation in, by diving-bell, 218. 

flooding has been diminished by 

works, 172. 



Clyde, improvements eiecatod on, and 
thair effects, 249. 

jetties, recommended by Golbonmo 

for, 249. 

low-water line, lowering of, 290, 

261. 

physical characteristics of, 337. 

quays, sections of, 261. 

velocity of surface ■ currents of, 

227. 

walls first proposed by Mr. Walker, 

186. 

walls largely used in lowar part of 

river, 249. 

weir at, qnestion as to its removal, 

252. 
Cochin, bar at, 272. 
Cofferdams, 220. 
Condamine, Mr., 168. 
Conon, river and tidal water in, 375. 

physical charsctetistics of, 337. 

Coode, Sir J., 215. 

Coquet river, physical charaoteriatio* of. 

Crib work, 146, 154. 

Crinan Canal, 28. 

Cromarty Firth, comparison of river and 

tidal water in, 276. 

under-currents, 1 1 5. 

cauae of, 122. 

Cross dredging 210. 

CubiU, Sir W., 14, 16, 144, 147, 150, 

213. 



Daks akd Locrh, 145. 

and flooding, 147. 

Danube, bar at, and works for its im- 
provement, 298. 

— ■ — physical characteriatics of, 297, 337. 

works executed for improvement of 

upper part of, 162. 

Datum line, 85. 

Deas, James, details of dredging and 
dredges at the ayde, 202. 

Dee (Aberdeenahire), diversion of. 



, 197. 
- method of obtaining Ei>ecimena of 



physical characteristics of, 337. 

nnder-onrrento of, 115, 124. 

Dee (Cheshire), bar, depth of water over, 
26S. 

bore on, 163, 164. 

deepest after winter floods, 192. 

jetties on, produce shoals and deep 



jvGoof^lc 



Dm, phyaical characteristics of, 337- 
— ■ — reclatnation of laud on, injnrioiu 

effect! of, 303. 
tidal linBfl of, variatioDH in, 76, 

103. 

relocitiea of anrface currents, 220. 

Deepening oE rivers. See Low-water. 

Deltas, formation of, 318. 

Depoaiti, depth of, aannally left on 

shores of estuaries, 319. 

in river*, natare and weight ot, 320. 

Denham, Captain. 223, 226, 317, 338. 

Dirki, M., 34. 

Discharge of rivers, 97, 107. 

method of determining, 98. 

eiclndJDg floods, 114. 

formulm for cftlcnlating, 105, 108. 

floods, 111. 

reqairei eoutrol in large rirer^ 1 35. 

DiTing'bell, excavati<ai by, 218. 

Docks, wet. 268. 

Dornoch Firth, caose of bar at, 267, 26S. 

tidal phenomena of, 67, 160. 

velocity of currents, 227. 

water, compwTBon of river and 

tidal water in, 277. 
Drainage of towpath* of canals, 18. 
of rivers, proportionate to areas of, 

134. 
Dredges, bag and s|ioon, 198. 

bucket, between two lighten, 199. 

Clyde, dimensions of, 204. 

hand, 201. 

silt pamp, 208, 200. 

steam, 200. 

■ improvements in, 207. 

Dredging, its introdnction, 108. 

— on Amsterdam and Sue* Canalfi by 

floating off dredgings, 209. 

on Clyde, tunonnt and cost of, 202. 

on Wear „ „ 207. 

hard materials require to be blasted 

before 212. 

cross, 210. 

longitudinal, 210. 

in exposed situations, 217. 

Dn Boat, 104, 106, 224. 

Epwabds, O., 213. 

EUet, C, 108, 136, 227, 203, 316, 337. 
Erne river, example of a river deficient 
in tidal capacity, 266. 

blasting in, 212. 

Everest, Rev. Mr., 337. 
Excavation by cofferdamt, 220. 
by diving-bell, 218. 






:, 152, 163. 



Floats for sscertuning anrhce currents, 

99. 

under-onrrenta, 117, 119, 120. 

Floatation, stones raised by, 219. 
Floods have a higher ratio to Ordinary 

discharge in small than lai^e rivers, 

114. 
discharge when ascertained should 

exclude. 111. 
water passing off different grounds 

during, 112, 113. 

gauging rivers exclusive of, 114. 

in MissisBippi, origin of, and works 

for prevention of, 139. 
river improvements tend to dimi- 
nish flooding, 171, 172. 

obatruotion to, by weirs, 147. 

Forth, barless river, 271. 

phygica] charscteristica of, 337. 

section of, showing present and 

former low-water lines, 239. 

tidal lines of, variations in, 83. 

phenomena before and after 

works, 240, 242. 
works executed for improvement of, 

and their effect, 238. 
Fossdvke Canal, 6. 

Fowler, John, 172, 189, 253, 254, 339. 
Foyle Bridge, bcoict produced by piers of, 

181. 
. river, physical charaoterisUcs of. 



- occurreuce in the sea, 130. 



specific gravity of fresh and salt 

water, 132. 
Frisi, P., 4, 105, 314. 

Gacsk, M., 209. 

Ganges, physical characteristics oE, 337. 

GarUck, £., 247. 

Gauge, tide, 75, 85. 

Ganging streams, 97. 

Gibb, J., 337. 

Okc^w quays, 261. 

Golboume, J., 249. 

Goole swing-bridge, 333. 

Gordon, L. D. B., 116, 322. 

Great Western Canal, perpendicular lift 

Green, J., 16. 

Grimsbaw, Mr., Sunderland, 200. 
Groynes or jetties in rivers objection- 
able, 176. 



□ iginzed by Google 



Gulf Strewn, 122. 

Hand sreikjes, kod dredging b^, 201. 
Hkrd bottom, bUating of, 212. 

ooScrdaiD BaitsbU for, 220. 

Harrowing, Bcoar fAcilitated by, 223. 
Harrison, T. E., 333. 
Hartlepool Slake, backwater, 27a. 
Hartley, Sir Cbarleu, 297, 337. 
Eawksbaw, J., 33, 37, 44, 182. 

J. C, 33. 

Healy, S., 20. 

Higb water not raised by facilitating 

tidal propagation, 170. 
Hilll^ Captain, 286, 268. 
Holland, canals in, 31. 
reclamation and protection of laod 

in, 325. 
Homer, L., 316, 338. 
Howdea, A., 113. 
Hndson river, 259. 
Hutcheson Bridge, 251. 
Hydraulic mean depth, 107. 
Hydrometric obaerTatiooH, 68. 
Hydrophores, difierent fornu of, and 

maDDet of nsing, 124. 

Ikcunbd flasks and perpendicolar lifts, 

0, 14, 16. 
Inverness Bridgs^ artifiinal bed for, 181. 
— — barboQT, groynes at, 259. 
Irrawaddf, materials held in suspeiuion 

by, 318. 

■ pbyncal cbaraeteristics of, 337. 

jAcsaov, G., 32, 151. 

Jlrdine, J., 63. 

Jeffreys, J. G., 119, 151. 

Jetties in rivers objectionable, 176. 

. beneficial results from removal of, 

179. 

Lakd benefited by ri 
311. 



r improvements. 



- works for protection of, in riven 
and estnaries, 322, 326, 327. 

reclamation of, 302. 

line of conserration proposed 

for, 324. 

depends on amonnt of mate- 
rials beld in suspension by rivers, 312. 

vegetation on, 321. 

marsh, level of, 321. 

section of manner of forma- 
tion of, 323. 



Laognedoc Canal, 6, 27. 
Lary Bridge, 180. 
Lep«re, M., 39. 
LeFerms, M., 209. 
Leslie, Sir John, 32, 108. 

A., 113. 

J., 15, 11^276. 

Lessept, F., 39. 

Leveliing by tjde-gaoges, 94. 

Locb Fleet, bard bar st, 300. 

Locks, canal, 3, 14. 

and danu on upper parts of navi- 

gatioDB, 145. 
Lcgin, T., 315, 316. 
Londonderry Bridge, 181. 

quays, 260- 

Longitndinal dredging^ 210. 

sectioDS, 94. 

Low-water line, lowering of, 324, 227, 

250, 305. 
Lune river channels, variations in, 183. 

low-water line, depression of, 305. 

physical characteristics of, 337, 338l 

tidal lines, variationB in, 79. 

tidal water, increaM of, hy woAi, 

306, 309. 

vorka executed for improvinj^ 347. 

LyeU, Sir C, 317. 
Lyster, G. F., 282. 

Mabsh lauds. Ste Land. 

Marcet, Dr., 130, 133. 

Materials, heaviest, next the sea in tddal 



ligbtott, do., in rivers, 314. 

held in suspension by diffeient 

rivers, 316. 
nature and weight of, in bed of 

Qyde, 316. 
siie of, capable of bmng csarried by 

rivers, 314. 
velocities of strouns oapable of 

carrying different kinds of, 315. 
Uean sea level, 63. 

velocities of rivers, 107. 

Meik, T., 273.'339. 

Mersey river bar, depth of water on, 265. 

cbangea of sand-banks and deptli of 

water on, 286- 
materials held in suspension by, 

318. 

physical oharsctorislacs of, 33S. 

velocity of tidal corrents in, 226. 

Wallasey Pool backwater, 280. 

Milne, J., 20, 22. 

Mississippi river bar, EUet's theory for 

formation of, 293. 
. delU of, 319. 



Digitized by Google 



MiwMcdppi, disoluirge of, Eliot's formobe 
for coIcuUting, 108, 138. 

drainafte, axei of, 141. 

Buteriallirouglit down by, 140,318. 

origiD of floods in, and worka pro- 
posed for preventiDg, 139, 140. 

plijiicAl diarscteristica of, 136. 

velocities of, 227. 

Mitchell, H., 94, 120, 322. 

MoakUnd Cftntd, iocimed pUne on, IS. 

MoDtrose basin, 279. 

Morris canal, do., 14. 

Muller, J., 3Z6. 

Murray, J., 207, 227. 

Natiqations, means used for rendering 
navigable apper part of, 143, 

crossing of, by railway bridges, 32S. 

stm water, 144. 

tunnelling ander, 330. 

Nest river, want of tidal capacity, 256. 

physical oharacteristics of, 338. 

Newry, 212. 

Niagara Falle, crib work used at, 164 
Nile, physical characteriHtiut of, 338. 
Nith river, pbyeical characteristics of, 338. 
North Holland canals, 31. 

OcBAK oiniBENTa, 122, 123. 
O'Connel, LieutenantColonsl, 113. 
Off-lets for canals, 17. 
Oldham, J., 325. 
Otter, Admiral, 226. 
Onse swing-bridge, 333. 

PiWC, P., 192, 24fl. 321, 338. 

Paton, J., 325. 

Pentlaod Firth, oocnrrence of fresh-water 

in. 132. 

velocity of tide oarrenta in, 226. 

Perpendicnlar lifts on canals, 14^ 15. 

Petemtan, A., 339. 

Pier« at entrances to riven to protect 

bars, 290, 398. 

sections of, 269, 

Pitcfaing of canal banks, 18, 21. 
Price, H., 253. 
Puddle for canals, 18. 



QUAIB, sections of ri 



r,260. 



Bankine, Professor, 10, 12, 13. 
Beclamation and protection of laud, 31 
Bendel, J. M., 14S, 180, 281. 
Bennie, Sir J., 1, 212, 330. 



318. 

Rhine, physical characteristics of, 338. 

works eieouted for improving upper 

portion of, 161. 

Rhodes, Thomas, 161. 

Rhone, {ihysical characterigtica of, 338. 

Ribble bar, depth of water over, 266. 

cofferdam used in, 220. 

low-water line, depression of, 306. 

physical characteristics of, 338. 

tidal soonr, land which might b« 

reclaimed vrithoot decreasing, 310. 

walls used on, 187, 247. 

works exBcated for improvement of, 

and their effects, 245. 

Richards, Admiral, 40, 47. 

River- proper comiMutment deQned and ita 
physical oharactemtiot described, 54. 

works for improvement of, 134. 

Rivers, different compartments o^ do- 
fined, 64. 

physical characteristics of, 337- 

Robertaon, O., 272. 

Robison, Professor, 67, 69, 108. 

Rodrigue:^ Manuel, 131. 

Rnsaell, John Scott, 19, 158, 163. 

St. Laweincb, steam-towing on, 26. 

Sabine, Sir K, 131. 

Sand-banks, ascertaining heights of, 92. 

changes in. See Bars. 

movement of, 289. 

Schuylkill, dams on, 146. 

Scour, formnln for oalonlating effective^ 



freshwater scour, 

deepens river*, 192. 

increased by river works, 226. 

keeps open sand bars, 274. 

land which mi(^t be reclaimed 

without decreamng, 310. 

bars said to originate from defi- 

<neut, 267. 



after storms. 



— beuefioial, a result of river works, 
28. 

— often results from hmited works, 226. 

— barrow need for faoiUtating, 223. 
F of backwater tor, 274, 



Sea-proper compartment of rivers, 64> 

262. 
Sectiona, cross and longitudinal, 94. 
Sectional area of barge canals, 13. 

of rivers, 107. 

enlargement of, beneficial, 183. 



Digitized b, Google 



346 IN] 

Severn, bore on, 166. 

bUating at, 212. 

wain on, 1*7. 

phyBcal chwaotervtica of, 338. 

silting at, 320. 

velocity of cnrrent in, 226, 

Shaouon, oblique weira on, Ifil. 

Shepherd, a., 162. 

Shingle, groynsg for leading, 2S9, 300. 

Ship cuwli, 27- 

Silt pnmp dredges, 2DS, 209. 

Simoni, Heean., improvementt in tteMD 

dredgea, 207. 
Slope in rivers, definition of, 107. 
rednoing the inielination of, 

224. 
limita of benefioial redootion 

of, 224. See. Forth, Tkj. 
Smeaton, J., 6, 27, 249. 
Smiles, S., 8. 
Smith, J., Belfast, 260. 
Soundings, datum for, 8S. 

formnhe for redadng, 88. 

high and low water, 91. 

rules for taking, 89. 

tide gauges used in reducing, 85, 

Spoon dredge, 198. 

Spratt, CaplBiD, 11 B, 

Stanches, 144. 

Steam dredging. Bee Dredging. 

towing on canals, 20, 

towing on rivers, 20, 25. 

SteveosoD, Alau, 116, 276. 
— Robert, 115, 124, 251, 253, 

Thomaa, 209. 

Still-water navigations, 144. 

Stones raised b; floatation, 219. 

Stopgates on canals, 6, 16. 

Stour, stanahes on, 144. 

Straight out ■ubstituted for bends in 

rivera, 196. 
Suez Canal, 39. 

dredging on, 209. 

tides in, 50. 

T&CHOMETEIl, 100. 

Tay river bar, depth of water, 266. 
changes on sandbanlu of, 286, 

2SS. 

bridge, scour prodnced by, 182. 

boulders raised by floatation, 219. 

currents, effect of grounded veasel 

in distorting, 178. 

velocity of, 226. 227. 

discharge in floods, 276. 

physical characteristics of, 339. 

scour prodnced by works, 235, 



Tayriver: land which might be redaimed 

without decreasing scoar, 310- 
slopes, relation of, to tidal ptoftr 

gstion, 242. 

subsidiary channels closed in, IM. 

tidal and river water, oomparison 

of, 276. 
pheoomena before and after woHu, 

234. 

works tor improvement of, and 

their beneficial effects, 229, 232. 

Tees, jetties and their effects, 253. 
straight cuts substituted for bends, 

196. 

walls at, 189. 

training walls eieoated and thdr 

beneficial effect, 253. 

flooding has been diminished by 

works, 172. 

physical charnoteristics of, 339. 

Telford, T., 9, 29, 143. 

Thames, physical ohancteristics at. 



173. 

bore, cause of, 163. 

curreuts, 161, 226. 

flow, importance and modification 

of, 166, 157. 

lines, Don-paralleliEiii of, 76. 

— phenomena of Dornoch Firth, 67. 

of Forth and Tay before and 

after works, 229. 

propagation, 156. 

" affected by slope, 169, 161. 

river works intended to faci- 

liUto, 169. 

high water not nused by faci- 
litating, 170. 

~ — range increase of, an effect of river 
works, 227. 

scour. See Sconring. 

— — wave, laws of its propagation, 158, 
244. 

obstacles which operate iu 

retarding, 162. 

Tide banns, 268. 

currents, velodties of, 226, 227. 

equalized by river works, 228. 

g*ngs". 7^ 86, 

duration of, increased by lowering 

low-water Une, 225, 228. 

Tide*, nature of inqniiy into, 73. 

anomalies of river, 69. 

observations, 68. 

selection of stations for observa- 
tions on, 76. 



Digitized by Google 



347 



Tides in Suez Cankl, SO. 

Towpatbs of canals, dramage of, 18. 

TrsiaiDg walls, 183. 

Taimalling uoder oavigationa, 336. 

Tweed, physical choracteriatics of, 339. 

Tyae, deptb nf water over bar, 265. 

physical charocterictics of, 339. 

Chdbrcurrbhts, lis. 
method of ascertwning, by tacho- 
meter, 116; by floats, 117. 

oauae of, 122. 

Ure, Mr., 20, 262, 387. 

Veqetation, level of, fint indic«tiotia 

of, 321. 
Velocities of cnireotB, 226. 

mode of determiuiDg, 98. 

Du Buat'B formula, 106, 109. See 

Discharge. 

of tide oairentB in rivers, 226. 

tab1« of gnrfoce, in different rivers, 

227. 
of atreama capable of carryiog 

materials, 3 IB- 
Vetch, Captain, 31. 
Vignolea, C., 6. 

Walker, J., 19, 186, 249, 261, 276. 
Wallasey Pool bachwater qneation, S80. 
Walls, truning, for guiding rivers, 186. 
B«ctioii of, 191. 



Warping or land-making, 312. 
Washington, Captain, 337. 
Waste weirs of canals, IS. 
Water supply for canals, 11. 
Water, density of fresh and salt, 124. 
under and superficial strata of, 

124. 
method of obtaining tpecimena of, 

from differeut depths, 124. 

e of fresh water in the sea, 



fresh and salt, specific gravity of, 

132. 

river and tidal, in estnaries, com- 
parison of, 2TG. 

Watt, James, 29. 

Waves cause sand bars, 267. 

Wear river bar, aiperiments to determine 
whence materials which form the bar 
are derived. 273. 

—~- bar, depth of water over, 265. 

dredging, quantity and cost of. 207. 

physical characteristics of, 339. 

piera to protect entrance to, 290. 

Weirs for upper navigations, 14S. 

obstruction presented by, 147. 

for public worka, 174. 

Wet docka, 258. 

Whewell, Dr., 171. 

Wrecks causa changes on aand bars, 288. 

TociNO,I>r. T., 187- 



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Digitized b, Google 



STEVENSON ON HARBOURS. 



In Om Fi/lume Svo, IllustraUd with fFoodculs and Pieties, Price 10*. 6d. 

HARBOURS 

THEIR DESIGN AND CONSTRUCTION. 

BT 

THOMAS STETENSON, F.E.S.E, M.r.C.E. 



" Thie work is undoubtedly of great Talue." — The Builder. 

" A most Talnable addition to tlie Engineers' library. The obapten 
devoted to ' Generation of WareB,' and to ' Force of Waves,' are admirable 
treatises." — The Artizan. 

" We know of no work &om wbioh an en^neering student is likely 
to derive more solid advantage tlian from this. Had we space we shonld 
gladly refer (o some of the more Btrikiag parte of the work ; we can, 
however, only refer to it as a whole, with onmixed commendation." — 
Pmtiiad Meehaniei Journal. 

"Mr. Stevenson has given us so much valuable matter in a condensed 
form in this book that we have not attempted to give anything like a 
synopeis of its contents ; to the student it will prove especially valuable." 
— Mechanici' Maganne, 

" Wo commend it to the oarefol and attentiTe perusal of all connected 
with the construcdon of harbours, dooks, and other kindred works of 
marine engineering." — Newea»tle Joumed, 

"The present work, by one who posseesea a most tiiorough and 
scientific knowledge of his subject, is likely to prove a valuable contribu- 
tion to marine engineering." — Qlaagow Herald. 

" This contribution to the library of the civil engineer may be con- 
ddered as a series of important facts, which should guide him in all hia 
proceedings." — Nauticcd Magazine. 



EDDTBUIiGH : ADAM AND CHARLES BLACK 



Digilizedby VjOOQI^ 



STEVENSON ON LiaHTHOUSE ILLUMINATION. 



Jtssi Pvhlished, in Demy 8tw, Second Edition, Price 1 2s. 6rf. 

LIGHTHOUSE ILLUMINATION 

BEING A DESCEIPTION OF THE HOLOPHOTAL SYSTEM, 

AND OF AZIMUTHAL, CONDENSING, AND OTHER 

NEW FORMS OF LIGHTHOUSE APPARATUS.' 

BY 

THOMAS STEVENSON, F.R.S.E., M.I.C.E., 

Illustrated wUh nunterous Woodcuts and Plates. 



Notices of First Edition. 

" It is DO mean merit to have advanced beyond so iUastriooB a pre- 
decessor as Frcsnel, but we oonclade the peruBal of the clear and interesting 
account before us, \rith tbe conviction that modern engineers of light- 
houses, and Mr. Stevenson pre-eminently among them, have sncoeeded 
in several important partieulars in improving and ext«ndiiig Fresnel's 
method. . . . The present work, besides being a summary account of 
established modem improvements of lighthouses, is valuable as a lucid 
and clear ezposiUon of the pore recent modifications of the author's 
valuable system of illnmination." — Civil Engineav' attd Architects 
Journal. 

" In the present instance, Mr. Thomas Stevenson has well reminded 
BB that he has not forgotten his combined engineering and literary craft ; 
for, whilst we can all of us go and ezamine his finished works, we can 
also, as the volume before us now tells us, turn to a scienUficaUy arranged 
book, wherein the whole system of ' lighthouse illumination ' is fully and 
carefully explained. . . . The book is one which tells all that is at 
present known on the difficult subject of applied optics for Uie transmia- 
aion of light lo great distances." — The Praciical Mechanic^ Journal. 

" Tbe perfect manner in which every particle of light is used in these 
days is in good keeping with the improvement which is everywhere seen. 
The object of the present Treatise is to explain the principles of the new 
system ; by which, as is shown by the author, the utmost can be obtained 
from a single source of light. We commend this highly approved inven- 
tion of Mr. Thomas Stevenson, with the valuable treatise in Weale's 
Library of Mr. Alan Stevenson, to the attention of those who wish for the 
best system of lighthouse illumination." — 37ic Navlicul Magazine. 



EDINBURGH : ADAM AND CHARLES BLACK. 



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In One Vol. QtMrto, cloth, UlustTated with n&trly Sixty Plates, and 
Two Hundred and Fifty Wood Engravings, price 30s., 

ARCHITECTURE 



AETS OF CONSTEUOTION, BUILDING, STONE-MASONEY, 

AECa, KOOF, JOINEKY, CAKPENTBY, AND 

STEENGTH OF MATEEIAI^. 

EDITED BT 

AETHUE ASHPITEL, F.S.A. 



rpHE ProprietorB of the " Encyclopedia Britankica" have published 
in B separate volume the Treatiees on Architecture and the Arts 
connected vith it, which appeared in that great national work, thus 
presenting in a convenient form for reference these admirable essays. 
The first of these, on ARCHITECTURE, BUILDING, and 
CONSTRUCTION, were written by the distinguished architect and 
engineer, WUHam Hosking, F.S.A. JOINERY and STONE- 
MASONRY were contribnted by Thomas Tredgold, whose name 
ifi a sufficient guarantee for the ezcellenco and value of his portion of 
the work. CARPENTRY was written by Thomas Young, an 
author of singularly varied attainments, and whose researches in science 
have placed him amongst the foremost men of the centnry. The accom- 
plished John Robison, Professor of Natural Philosophy in 
the University of Edinburgh, contribnted the Treatises on 
ROOF, ARCH, and STRENGTH of MATERIALS, and im- 
portant additions have been made by Robert Stephenson and the 
Editor, whose name is on the title-page. Besides the valnable material 
thns provided for the Library of the architect, the Editor, availing him- 
self of researches and discoveries, has supplemented the articles on 



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ARCHITECTURE— conftnwed. 

EGYPTIAN, JEWISH, and ASSYRIAN ARCHITEC- 
TURE, has added a chapter on INDIAN and CHINESE archi- 
tetJture, has written a new and valuable Glossary of the terma of 
Mediceval Architectare, with sixteen plates, containing nearly 300 
illustrations of the Arabic, Romanesque, and Pointed styles. 
The chapter on ACOUSTICS is also a raluabla addition, and he has 
brought down the information on Joineiy, Boot, Stone- Maaonry, etc^ to 
the present time. The whole is contained in one volume, 
printed in double columns in a clear type ; and fifom 
the statement which we have given of its contents, the 
architect and student of architecture must perceive that 
this is a valuable addition to the literature of their 
profession or study. The w^ork is indeed a library in 
itself, and brings together in a convenient shape the 
material of many separate publications. 

To the etodent of architecture we wonld especially lecommend this 
volume. If he would read carefully the sage advice given by Mr. 
Hosking on the study of bis profession, and the qnalificatiuua of a true 
architect; if be will conscientiously follow ont that advice, and profit 
indnatrionely by the varied infonnatioD afforded on the theory and prac- 
tice of his art, with reasonable abilities, he will undoubtedly achieve 
success. It is in the aid which this publication offers to the student 
that we regard it as especially important. It is of value to the archi- 
tect, builder, and the various tradesmen who labour under these, but it 
is a text-book for the stndent. Written by a clever and judicious 
architect, who, by his own energy, reached a distinguished pontiou, it 
gives the results of his experience, and is a safe guide to the young 
architect wbe seeks to master a profession, which, of all professions, is 
perhaps that which requires the most varied attainments, cultivated 
taste, and accurate knowledge. The remarks upon the origin and his- 
tory of architecture are agreeably written, and contain much valuable 
information. The history of his art, and of the lives of eminent archi- 
tects, ought to be special portions of every young architect's study- 
might, indeed, we think, be a nsefnl part of the study of every one. So 



n.„-,7=dbvG00f^lc 



AECHITECTURE— con(HH«d. 

tnncb do we feel tbU to be the case, tliat we recommend the present 
work to maeterB of scbools and other senunaiieB of learning. luHtraction 
in the rndiments of architecture onght undoubtedly to be given in all 
schools ; it is BO, in a very useful manner, to oar personal knowledge, in 
some in Ireland, having ourselves examined the youthful pupils, and 
ascertained that they had a &ir knowledge of the orders of architecture 
and the component parts of buildings. This useful practical study is 
far too much neglected in schools throughout England and Scotland. 
With the aid of the Treatise on Architecture which we are reviewing, 
this neglect might be remedied. It is only by the careful study of the 
history of architecture, in such works as the present, and by ito monu- 
ments, that taste, discrimination, and a sound common-sense view of the 
whole subject can be attained. 

We have dwelt at so great length upon the first portion of this useful 
volume that we have but little space left for the consideration of the 
remainder of its contents. These are so essentially of a technical 
character that we cannot hope to make them Interesting to the generality 
of our readers. To the professional man they are invalu- 
able ; and brought together, as they are, in one volume, 
they constitute excellent chapters for reference on almost 
every conceivable subject relating to the practice of 
Architecture. 

The author has succeeded in ^ving interest to the detuls of his 
subjects Construction and Building, by bis remarks on foreign construe- ' 
tioD, and by comparisons between it and our own methods he exhibits a 
large and unprejudiced mind ; and these portions of his treatise are very 
suggestive of the preparation of the students for profitable foreign travel. 
The instruction given in practical details is so minute, so clearly 
expressed, and brought together in so interesting a manner, that all 
may read with profit 

Both in its historic and sdentific aspect the treatise on the Arch is 
a valuable contribution, and the engineer as well as the architect may 



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ASGHITECTUBE— cantmuet^. 

STail himself of the iDformatioa contained. In the article Roof, the 
principles explwned and the illiutraljons given are valoable. Many of 
these last have appeared elsewhere ; but they are here brong^ht together 
in a usefiil, practical vaj, forming an excellent work of reference, whilst 
the principlea are described in snch clear and explicit langoage, that the 
most yonthfal stndent, if commonly attentive, may nndentaad them. 
A treatise on Strength of Materials completes this nsefol Tolnme. We 
may add, that the Illustrations are well executed and 
copious; and these, aided by the excellent Glossary of 
Architectural Terms, constitute a work so complete in 
its design and execution, that we have great pleasure 
In reconunending It to the professor and amateur, to the 
collie, school, and workshop. — Qkugow Herald. 

The moil valuable addidon, however, made by the Editor, is a Glos- 
sary of the terms in Medieval Archlteotnre, and dxteen new Plates, 
illnstrating nearly three hnndred subjects, many of them never pnbliahed 
before. This Glossary fills thirty new pages, and Bhons mnch care, 
research, and learning. The volume will make an excellent prize-book 
for Architectural Societies and Colleges. —Builder. 

Whoever wants to give his pupils or apprentices a really good text- 
book upon the arts of oonstmc^n, we would recommend to him thii 
publication. — Buildert' Trade Ctreular. 



EDINBIJKGH : ADAM & CHARLES BLACK 
JAN 1 "^ 1Q20 



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